table: implement write sets for insert_many

rpc_helper: don't use tokio::spawn for individual requests
layout: refactor digests and add "!=" assertions before epidemic bcast
2023-11-16 16:41:45 +01:00 · 2023-11-16 16:34:01 +01:00 · 2023-11-16 13:51:40 +01:00 · 2023-11-16 13:26:43 +01:00 · 2023-11-15 15:56:57 +01:00 · 2023-11-15 15:40:44 +01:00
39 changed files with 2410 additions and 1448 deletions
--- a/src/api/admin/api_server.rs
+++ b/src/api/admin/api_server.rs
@ -279,7 +279,7 @@ impl ApiHandler for AdminApiServer {
 			Endpoint::GetClusterLayout => handle_get_cluster_layout(&self.garage).await,
 			Endpoint::UpdateClusterLayout => handle_update_cluster_layout(&self.garage, req).await,
 			Endpoint::ApplyClusterLayout => handle_apply_cluster_layout(&self.garage, req).await,
-			Endpoint::RevertClusterLayout => handle_revert_cluster_layout(&self.garage, req).await,
+			Endpoint::RevertClusterLayout => handle_revert_cluster_layout(&self.garage).await,
 			// Keys
 			Endpoint::ListKeys => handle_list_keys(&self.garage).await,
 			Endpoint::GetKeyInfo {
--- a/src/api/admin/bucket.rs
+++ b/src/api/admin/bucket.rs
@ -122,7 +122,7 @@ async fn bucket_info_results(
 		.table
 		.get(&bucket_id, &EmptyKey)
 		.await?
-		.map(|x| x.filtered_values(&garage.system.ring.borrow()))
+		.map(|x| x.filtered_values(&garage.system.cluster_layout()))
 		.unwrap_or_default();
 	let mpu_counters = garage
@ -130,7 +130,7 @@ async fn bucket_info_results(
 		.table
 		.get(&bucket_id, &EmptyKey)
 		.await?
-		.map(|x| x.filtered_values(&garage.system.ring.borrow()))
+		.map(|x| x.filtered_values(&garage.system.cluster_layout()))
 		.unwrap_or_default();
 	let mut relevant_keys = HashMap::new();
--- a/src/api/admin/cluster.rs
+++ b/src/api/admin/cluster.rs
@ -33,7 +33,7 @@ pub async fn handle_get_cluster_status(garage: &Arc<Garage>) -> Result<Response<
 				hostname: i.status.hostname,
 			})
 			.collect(),
-		layout: format_cluster_layout(&garage.system.get_cluster_layout()),
+		layout: format_cluster_layout(&garage.system.cluster_layout()),
 	};
 	Ok(json_ok_response(&res)?)
@ -84,13 +84,14 @@ pub async fn handle_connect_cluster_nodes(
 }
 pub async fn handle_get_cluster_layout(garage: &Arc<Garage>) -> Result<Response<Body>, Error> {
-	let res = format_cluster_layout(&garage.system.get_cluster_layout());
+	let res = format_cluster_layout(&garage.system.cluster_layout());
 	Ok(json_ok_response(&res)?)
 }
-fn format_cluster_layout(layout: &layout::ClusterLayout) -> GetClusterLayoutResponse {
+fn format_cluster_layout(layout: &layout::LayoutHistory) -> GetClusterLayoutResponse {
 	let roles = layout
 		.current()
 		.roles
 		.items()
 		.iter()
@ -104,10 +105,12 @@ fn format_cluster_layout(layout: &layout::ClusterLayout) -> GetClusterLayoutResp
 		.collect::<Vec<_>>();
 	let staged_role_changes = layout
-		.staging_roles
+		.staging
 		.get()
 		.roles
 		.items()
 		.iter()
-		.filter(|(k, _, v)| layout.roles.get(k) != Some(v))
+		.filter(|(k, _, v)| layout.current().roles.get(k) != Some(v))
 		.map(|(k, _, v)| match &v.0 {
 			None => NodeRoleChange {
 				id: hex::encode(k),
@ -125,7 +128,7 @@ fn format_cluster_layout(layout: &layout::ClusterLayout) -> GetClusterLayoutResp
 		.collect::<Vec<_>>();
 	GetClusterLayoutResponse {
-		version: layout.version,
+		version: layout.current().version,
 		roles,
 		staged_role_changes,
 	}
@ -207,10 +210,10 @@ pub async fn handle_update_cluster_layout(
 ) -> Result<Response<Body>, Error> {
 	let updates = parse_json_body::<UpdateClusterLayoutRequest>(req).await?;
-	let mut layout = garage.system.get_cluster_layout();
+	let mut layout = garage.system.cluster_layout().clone();
-	let mut roles = layout.roles.clone();
+	let mut roles = layout.current().roles.clone();
-	roles.merge(&layout.staging_roles);
+	roles.merge(&layout.staging.get().roles);
 	for change in updates {
 		let node = hex::decode(&change.id).ok_or_bad_request("Invalid node identifier")?;
@ -231,11 +234,17 @@ pub async fn handle_update_cluster_layout(
 		};
 		layout
-			.staging_roles
+			.staging
 			.get_mut()
 			.roles
 			.merge(&roles.update_mutator(node, layout::NodeRoleV(new_role)));
 	}
-	garage.system.update_cluster_layout(&layout).await?;
+	garage
 		.system
 		.layout_manager
 		.update_cluster_layout(&layout)
 		.await?;
 	let res = format_cluster_layout(&layout);
 	Ok(json_ok_response(&res)?)
@ -245,12 +254,16 @@ pub async fn handle_apply_cluster_layout(
 	garage: &Arc<Garage>,
 	req: Request<Body>,
 ) -> Result<Response<Body>, Error> {
-	let param = parse_json_body::<ApplyRevertLayoutRequest>(req).await?;
+	let param = parse_json_body::<ApplyLayoutRequest>(req).await?;
-	let layout = garage.system.get_cluster_layout();
+	let layout = garage.system.cluster_layout().clone();
 	let (layout, msg) = layout.apply_staged_changes(Some(param.version))?;
-	garage.system.update_cluster_layout(&layout).await?;
+	garage
 		.system
 		.layout_manager
 		.update_cluster_layout(&layout)
 		.await?;
 	let res = ApplyClusterLayoutResponse {
 		message: msg,
@ -259,15 +272,14 @@ pub async fn handle_apply_cluster_layout(
 	Ok(json_ok_response(&res)?)
 }
-pub async fn handle_revert_cluster_layout(
+pub async fn handle_revert_cluster_layout(garage: &Arc<Garage>) -> Result<Response<Body>, Error> {
-	garage: &Arc<Garage>,
+	let layout = garage.system.cluster_layout().clone();
-	req: Request<Body>,
+	let layout = layout.revert_staged_changes()?;
-) -> Result<Response<Body>, Error> {
+	garage
-	let param = parse_json_body::<ApplyRevertLayoutRequest>(req).await?;
+		.system
-
+		.layout_manager
-	let layout = garage.system.get_cluster_layout();
+		.update_cluster_layout(&layout)
-	let layout = layout.revert_staged_changes(Some(param.version))?;
+		.await?;
 	garage.system.update_cluster_layout(&layout).await?;
 	let res = format_cluster_layout(&layout);
 	Ok(json_ok_response(&res)?)
@ -279,7 +291,7 @@ type UpdateClusterLayoutRequest = Vec<NodeRoleChange>;
 #[derive(Deserialize)]
 #[serde(rename_all = "camelCase")]
-struct ApplyRevertLayoutRequest {
+struct ApplyLayoutRequest {
 	version: u64,
 }
--- a/src/api/common_error.rs
+++ b/src/api/common_error.rs
@ -53,9 +53,7 @@ impl CommonError {
 	pub fn http_status_code(&self) -> StatusCode {
 		match self {
 			CommonError::InternalError(
-				GarageError::Timeout
+				GarageError::Timeout | GarageError::RemoteError(_) | GarageError::Quorum(..),
 				| GarageError::RemoteError(_)
 				| GarageError::Quorum(_, _, _, _),
 			) => StatusCode::SERVICE_UNAVAILABLE,
 			CommonError::InternalError(_) | CommonError::Hyper(_) | CommonError::Http(_) => {
 				StatusCode::INTERNAL_SERVER_ERROR
@ -72,9 +70,7 @@ impl CommonError {
 		match self {
 			CommonError::Forbidden(_) => "AccessDenied",
 			CommonError::InternalError(
-				GarageError::Timeout
+				GarageError::Timeout | GarageError::RemoteError(_) | GarageError::Quorum(..),
 				| GarageError::RemoteError(_)
 				| GarageError::Quorum(_, _, _, _),
 			) => "ServiceUnavailable",
 			CommonError::InternalError(_) | CommonError::Hyper(_) | CommonError::Http(_) => {
 				"InternalError"
--- a/src/api/k2v/index.rs
+++ b/src/api/k2v/index.rs
@ -5,7 +5,6 @@ use serde::Serialize;
 use garage_util::data::*;
 use garage_rpc::ring::Ring;
 use garage_table::util::*;
 use garage_model::garage::Garage;
@ -26,7 +25,11 @@ pub async fn handle_read_index(
 ) -> Result<Response<Body>, Error> {
 	let reverse = reverse.unwrap_or(false);
-	let ring: Arc<Ring> = garage.system.ring.borrow().clone();
+	let node_id_vec = garage
 		.system
 		.cluster_layout()
 		.all_nongateway_nodes()
 		.to_vec();
 	let (partition_keys, more, next_start) = read_range(
 		&garage.k2v.counter_table.table,
@ -35,7 +38,7 @@ pub async fn handle_read_index(
 		&start,
 		&end,
 		limit,
-		Some((DeletedFilter::NotDeleted, ring.layout.node_id_vec.clone())),
+		Some((DeletedFilter::NotDeleted, node_id_vec)),
 		EnumerationOrder::from_reverse(reverse),
 	)
 	.await?;
@ -54,7 +57,7 @@ pub async fn handle_read_index(
 		partition_keys: partition_keys
 			.into_iter()
 			.map(|part| {
-				let vals = part.filtered_values(&ring);
+				let vals = part.filtered_values(&garage.system.cluster_layout());
 				ReadIndexResponseEntry {
 					pk: part.sk,
 					entries: *vals.get(&s_entries).unwrap_or(&0),
--- a/src/api/s3/put.rs
+++ b/src/api/s3/put.rs
@ -253,7 +253,7 @@ pub(crate) async fn check_quotas(
 		.await?;
 	let counters = counters
-		.map(|x| x.filtered_values(&garage.system.ring.borrow()))
+		.map(|x| x.filtered_values(&garage.system.cluster_layout()))
 		.unwrap_or_default();
 	let (prev_cnt_obj, prev_cnt_size) = match prev_object {
--- a/src/block/manager.rs
+++ b/src/block/manager.rs
@ -265,7 +265,7 @@ impl BlockManager {
 		Fut: futures::Future<Output = Result<T, Error>>,
 	{
 		let who = self.replication.read_nodes(hash);
-		let who = self.system.rpc.request_order(&who);
+		let who = self.system.rpc_helper().request_order(&who);
 		for node in who.iter() {
 			let node_id = NodeID::from(*node);
@ -305,7 +305,7 @@ impl BlockManager {
 				// if the first one doesn't succeed rapidly
 				// TODO: keep first request running when initiating a new one and take the
 				// one that finishes earlier
-				_ = tokio::time::sleep(self.system.rpc.rpc_timeout()) => {
+				_ = tokio::time::sleep(self.system.rpc_helper().rpc_timeout()) => {
 					debug!("Get block {:?}: node {:?} didn't return block in time, trying next.", hash, node);
 				}
 			};
@ -354,7 +354,7 @@ impl BlockManager {
 	/// Send block to nodes that should have it
 	pub async fn rpc_put_block(&self, hash: Hash, data: Bytes) -> Result<(), Error> {
-		let who = self.replication.write_nodes(&hash);
+		let who = self.replication.write_sets(&hash);
 		let (header, bytes) = DataBlock::from_buffer(data, self.compression_level)
 			.await
@ -363,10 +363,10 @@ impl BlockManager {
 			Req::new(BlockRpc::PutBlock { hash, header })?.with_stream_from_buffer(bytes);
 		self.system
-			.rpc
+			.rpc_helper()
-			.try_call_many(
+			.try_write_many_sets(
 				&self.endpoint,
-				&who[..],
+				who.as_ref(),
 				put_block_rpc,
 				RequestStrategy::with_priority(PRIO_NORMAL | PRIO_SECONDARY)
 					.with_quorum(self.replication.write_quorum()),
@ -439,7 +439,7 @@ impl BlockManager {
 			tokio::spawn(async move {
 				if let Err(e) = this
 					.resync
-					.put_to_resync(&hash, 2 * this.system.rpc.rpc_timeout())
+					.put_to_resync(&hash, 2 * this.system.rpc_helper().rpc_timeout())
 				{
 					error!("Block {:?} could not be put in resync queue: {}.", hash, e);
 				}
@ -533,7 +533,7 @@ impl BlockManager {
 				None => {
 					// Not found but maybe we should have had it ??
 					self.resync
-						.put_to_resync(hash, 2 * self.system.rpc.rpc_timeout())?;
+						.put_to_resync(hash, 2 * self.system.rpc_helper().rpc_timeout())?;
 					return Err(Error::Message(format!(
 						"block {:?} not found on node",
 						hash
--- a/src/block/resync.rs
+++ b/src/block/resync.rs
@ -377,7 +377,7 @@ impl BlockResyncManager {
 			info!("Resync block {:?}: offloading and deleting", hash);
 			let existing_path = existing_path.unwrap();
-			let mut who = manager.replication.write_nodes(hash);
+			let mut who = manager.replication.storage_nodes(hash);
 			if who.len() < manager.replication.write_quorum() {
 				return Err(Error::Message("Not trying to offload block because we don't have a quorum of nodes to write to".to_string()));
 			}
@ -385,7 +385,7 @@ impl BlockResyncManager {
 			let who_needs_resps = manager
 				.system
-				.rpc
+				.rpc_helper()
 				.call_many(
 					&manager.endpoint,
 					&who,
@ -431,10 +431,10 @@ impl BlockResyncManager {
 				.with_stream_from_buffer(bytes);
 				manager
 					.system
-					.rpc
+					.rpc_helper()
 					.try_call_many(
 						&manager.endpoint,
-						&need_nodes[..],
+						&need_nodes,
 						put_block_message,
 						RequestStrategy::with_priority(PRIO_BACKGROUND)
 							.with_quorum(need_nodes.len()),
--- a/src/garage/admin/bucket.rs
+++ b/src/garage/admin/bucket.rs
@ -70,7 +70,7 @@ impl AdminRpcHandler {
 			.table
 			.get(&bucket_id, &EmptyKey)
 			.await?
-			.map(|x| x.filtered_values(&self.garage.system.ring.borrow()))
+			.map(|x| x.filtered_values(&self.garage.system.cluster_layout()))
 			.unwrap_or_default();
 		let mpu_counters = self
@ -79,7 +79,7 @@ impl AdminRpcHandler {
 			.table
 			.get(&bucket_id, &EmptyKey)
 			.await?
-			.map(|x| x.filtered_values(&self.garage.system.ring.borrow()))
+			.map(|x| x.filtered_values(&self.garage.system.cluster_layout()))
 			.unwrap_or_default();
 		let mut relevant_keys = HashMap::new();
--- a/src/garage/admin/mod.rs
+++ b/src/garage/admin/mod.rs
@ -18,7 +18,7 @@ use garage_util::error::Error as GarageError;
 use garage_table::replication::*;
 use garage_table::*;
-use garage_rpc::ring::PARTITION_BITS;
+use garage_rpc::layout::PARTITION_BITS;
 use garage_rpc::*;
 use garage_block::manager::BlockResyncErrorInfo;
@ -126,8 +126,8 @@ impl AdminRpcHandler {
 			opt_to_send.all_nodes = false;
 			let mut failures = vec![];
-			let ring = self.garage.system.ring.borrow().clone();
+			let all_nodes = self.garage.system.cluster_layout().all_nodes().to_vec();
-			for node in ring.layout.node_ids().iter() {
+			for node in all_nodes.iter() {
 				let node = (*node).into();
 				let resp = self
 					.endpoint
@ -163,9 +163,9 @@ impl AdminRpcHandler {
 	async fn handle_stats(&self, opt: StatsOpt) -> Result<AdminRpc, Error> {
 		if opt.all_nodes {
 			let mut ret = String::new();
-			let ring = self.garage.system.ring.borrow().clone();
+			let all_nodes = self.garage.system.cluster_layout().all_nodes().to_vec();
-			for node in ring.layout.node_ids().iter() {
+			for node in all_nodes.iter() {
 				let mut opt = opt.clone();
 				opt.all_nodes = false;
 				opt.skip_global = true;
@ -275,10 +275,11 @@ impl AdminRpcHandler {
 		let mut ret = String::new();
 		// Gather storage node and free space statistics
-		let layout = &self.garage.system.ring.borrow().layout;
+		// TODO: not only layout.current() ???
 		let layout = &self.garage.system.cluster_layout();
 		let mut node_partition_count = HashMap::<Uuid, u64>::new();
-		for short_id in layout.ring_assignment_data.iter() {
+		for short_id in layout.current().ring_assignment_data.iter() {
-			let id = layout.node_id_vec[*short_id as usize];
+			let id = layout.current().node_id_vec[*short_id as usize];
 			*node_partition_count.entry(id).or_default() += 1;
 		}
 		let node_info = self
@ -293,7 +294,7 @@ impl AdminRpcHandler {
 		for (id, parts) in node_partition_count.iter() {
 			let info = node_info.get(id);
 			let status = info.map(|x| &x.status);
-			let role = layout.roles.get(id).and_then(|x| x.0.as_ref());
+			let role = layout.current().roles.get(id).and_then(|x| x.0.as_ref());
 			let hostname = status.map(|x| x.hostname.as_str()).unwrap_or("?");
 			let zone = role.map(|x| x.zone.as_str()).unwrap_or("?");
 			let capacity = role
@ -440,8 +441,8 @@ impl AdminRpcHandler {
 	) -> Result<AdminRpc, Error> {
 		if all_nodes {
 			let mut ret = vec![];
-			let ring = self.garage.system.ring.borrow().clone();
+			let all_nodes = self.garage.system.cluster_layout().all_nodes().to_vec();
-			for node in ring.layout.node_ids().iter() {
+			for node in all_nodes.iter() {
 				let node = (*node).into();
 				match self
 					.endpoint
@ -488,8 +489,8 @@ impl AdminRpcHandler {
 	) -> Result<AdminRpc, Error> {
 		if all_nodes {
 			let mut ret = vec![];
-			let ring = self.garage.system.ring.borrow().clone();
+			let all_nodes = self.garage.system.cluster_layout().all_nodes().to_vec();
-			for node in ring.layout.node_ids().iter() {
+			for node in all_nodes.iter() {
 				let node = (*node).into();
 				match self
 					.endpoint
--- a/src/garage/cli/cmd.rs
+++ b/src/garage/cli/cmd.rs
@ -62,7 +62,7 @@ pub async fn cmd_status(rpc_cli: &Endpoint<SystemRpc, ()>, rpc_host: NodeID) ->
 	let mut healthy_nodes =
 		vec!["ID\tHostname\tAddress\tTags\tZone\tCapacity\tDataAvail".to_string()];
 	for adv in status.iter().filter(|adv| adv.is_up) {
-		match layout.roles.get(&adv.id) {
+		match layout.current().roles.get(&adv.id) {
 			Some(NodeRoleV(Some(cfg))) => {
 				let data_avail = match &adv.status.data_disk_avail {
 					_ if cfg.capacity.is_none() => "N/A".into(),
@ -85,7 +85,7 @@ pub async fn cmd_status(rpc_cli: &Endpoint<SystemRpc, ()>, rpc_host: NodeID) ->
 				));
 			}
 			_ => {
-				let new_role = match layout.staging_roles.get(&adv.id) {
+				let new_role = match layout.staging.get().roles.get(&adv.id) {
 					Some(NodeRoleV(Some(_))) => "(pending)",
 					_ => "NO ROLE ASSIGNED",
 				};
@ -102,10 +102,15 @@ pub async fn cmd_status(rpc_cli: &Endpoint<SystemRpc, ()>, rpc_host: NodeID) ->
 	format_table(healthy_nodes);
 	let status_keys = status.iter().map(|adv| adv.id).collect::<HashSet<_>>();
-	let failure_case_1 = status
+	let failure_case_1 = status.iter().any(|adv| {
-		.iter()
+		!adv.is_up
-		.any(|adv| !adv.is_up && matches!(layout.roles.get(&adv.id), Some(NodeRoleV(Some(_)))));
+			&& matches!(
 				layout.current().roles.get(&adv.id),
 				Some(NodeRoleV(Some(_)))
 			)
 	});
 	let failure_case_2 = layout
 		.current()
 		.roles
 		.items()
 		.iter()
@ -115,7 +120,7 @@ pub async fn cmd_status(rpc_cli: &Endpoint<SystemRpc, ()>, rpc_host: NodeID) ->
 		let mut failed_nodes =
 			vec!["ID\tHostname\tAddress\tTags\tZone\tCapacity\tLast seen".to_string()];
 		for adv in status.iter().filter(|adv| !adv.is_up) {
-			if let Some(NodeRoleV(Some(cfg))) = layout.roles.get(&adv.id) {
+			if let Some(NodeRoleV(Some(cfg))) = layout.current().roles.get(&adv.id) {
 				let tf = timeago::Formatter::new();
 				failed_nodes.push(format!(
 					"{id:?}\t{host}\t{addr}\t[{tags}]\t{zone}\t{capacity}\t{last_seen}",
@ -132,7 +137,7 @@ pub async fn cmd_status(rpc_cli: &Endpoint<SystemRpc, ()>, rpc_host: NodeID) ->
 				));
 			}
 		}
-		for (id, _, role_v) in layout.roles.items().iter() {
+		for (id, _, role_v) in layout.current().roles.items().iter() {
 			if let NodeRoleV(Some(cfg)) = role_v {
 				if !status_keys.contains(id) {
 					failed_nodes.push(format!(
--- a/src/garage/cli/layout.rs
+++ b/src/garage/cli/layout.rs
@ -49,6 +49,7 @@ pub async fn cmd_assign_role(
 	};
 	let mut layout = fetch_layout(rpc_cli, rpc_host).await?;
 	let all_nodes = layout.get_all_nodes();
 	let added_nodes = args
 		.node_ids
@ -58,21 +59,23 @@ pub async fn cmd_assign_role(
 				status
 					.iter()
 					.map(|adv| adv.id)
-					.chain(layout.node_ids().iter().cloned()),
+					.chain(all_nodes.iter().cloned()),
 				node_id,
 			)
 		})
 		.collect::<Result<Vec<_>, _>>()?;
-	let mut roles = layout.roles.clone();
+	let mut roles = layout.current().roles.clone();
-	roles.merge(&layout.staging_roles);
+	roles.merge(&layout.staging.get().roles);
 	for replaced in args.replace.iter() {
-		let replaced_node = find_matching_node(layout.node_ids().iter().cloned(), replaced)?;
+		let replaced_node = find_matching_node(all_nodes.iter().cloned(), replaced)?;
 		match roles.get(&replaced_node) {
 			Some(NodeRoleV(Some(_))) => {
 				layout
-					.staging_roles
+					.staging
 					.get_mut()
 					.roles
 					.merge(&roles.update_mutator(replaced_node, NodeRoleV(None)));
 			}
 			_ => {
@ -130,7 +133,9 @@ pub async fn cmd_assign_role(
 		};
 		layout
-			.staging_roles
+			.staging
 			.get_mut()
 			.roles
 			.merge(&roles.update_mutator(added_node, NodeRoleV(Some(new_entry))));
 	}
@ -149,14 +154,16 @@ pub async fn cmd_remove_role(
 ) -> Result<(), Error> {
 	let mut layout = fetch_layout(rpc_cli, rpc_host).await?;
-	let mut roles = layout.roles.clone();
+	let mut roles = layout.current().roles.clone();
-	roles.merge(&layout.staging_roles);
+	roles.merge(&layout.staging.get().roles);
 	let deleted_node =
 		find_matching_node(roles.items().iter().map(|(id, _, _)| *id), &args.node_id)?;
 	layout
-		.staging_roles
+		.staging
 		.get_mut()
 		.roles
 		.merge(&roles.update_mutator(deleted_node, NodeRoleV(None)));
 	send_layout(rpc_cli, rpc_host, layout).await?;
@ -174,13 +181,16 @@ pub async fn cmd_show_layout(
 	let layout = fetch_layout(rpc_cli, rpc_host).await?;
 	println!("==== CURRENT CLUSTER LAYOUT ====");
-	print_cluster_layout(&layout, "No nodes currently have a role in the cluster.\nSee `garage status` to view available nodes.");
+	print_cluster_layout(layout.current(), "No nodes currently have a role in the cluster.\nSee `garage status` to view available nodes.");
 	println!();
-	println!("Current cluster layout version: {}", layout.version);
+	println!(
 		"Current cluster layout version: {}",
 		layout.current().version
 	);
 	let has_role_changes = print_staging_role_changes(&layout);
 	if has_role_changes {
-		let v = layout.version;
+		let v = layout.current().version;
 		let res_apply = layout.apply_staged_changes(Some(v + 1));
 		// this will print the stats of what partitions
@ -189,7 +199,7 @@ pub async fn cmd_show_layout(
 			Ok((layout, msg)) => {
 				println!();
 				println!("==== NEW CLUSTER LAYOUT AFTER APPLYING CHANGES ====");
-				print_cluster_layout(&layout, "No nodes have a role in the new layout.");
+				print_cluster_layout(layout.current(), "No nodes have a role in the new layout.");
 				println!();
 				for line in msg.iter() {
@ -199,16 +209,12 @@ pub async fn cmd_show_layout(
 				println!();
 				println!("    garage layout apply --version {}", v + 1);
 				println!();
-				println!(
+				println!("You can also revert all proposed changes with: garage layout revert");
                    "You can also revert all proposed changes with: garage layout revert --version {}",
                    v + 1)
 			}
 			Err(e) => {
 				println!("Error while trying to compute the assignment: {}", e);
 				println!("This new layout cannot yet be applied.");
-				println!(
+				println!("You can also revert all proposed changes with: garage layout revert");
                    "You can also revert all proposed changes with: garage layout revert --version {}",
                    v + 1)
 			}
 		}
 	}
@ -241,9 +247,15 @@ pub async fn cmd_revert_layout(
 	rpc_host: NodeID,
 	revert_opt: RevertLayoutOpt,
 ) -> Result<(), Error> {
 	if !revert_opt.yes {
 		return Err(Error::Message(
 			"Please add the --yes flag to run the layout revert operation".into(),
 		));
 	}
 	let layout = fetch_layout(rpc_cli, rpc_host).await?;
-	let layout = layout.revert_staged_changes(revert_opt.version)?;
+	let layout = layout.revert_staged_changes()?;
 	send_layout(rpc_cli, rpc_host, layout).await?;
@ -266,11 +278,11 @@ pub async fn cmd_config_layout(
 				.parse::<ZoneRedundancy>()
 				.ok_or_message("invalid zone redundancy value")?;
 			if let ZoneRedundancy::AtLeast(r_int) = r {
-				if r_int > layout.replication_factor {
+				if r_int > layout.current().replication_factor {
 					return Err(Error::Message(format!(
 						"The zone redundancy must be smaller or equal to the \
                    replication factor ({}).",
-						layout.replication_factor
+						layout.current().replication_factor
 					)));
 				} else if r_int < 1 {
 					return Err(Error::Message(
@ -280,7 +292,9 @@ pub async fn cmd_config_layout(
 			}
 			layout
-				.staging_parameters
+				.staging
 				.get_mut()
 				.parameters
 				.update(LayoutParameters { zone_redundancy: r });
 			println!("The zone redundancy parameter has been set to '{}'.", r);
 			did_something = true;
@ -302,7 +316,7 @@ pub async fn cmd_config_layout(
 pub async fn fetch_layout(
 	rpc_cli: &Endpoint<SystemRpc, ()>,
 	rpc_host: NodeID,
-) -> Result<ClusterLayout, Error> {
+) -> Result<LayoutHistory, Error> {
 	match rpc_cli
 		.call(&rpc_host, SystemRpc::PullClusterLayout, PRIO_NORMAL)
 		.await??
@ -315,7 +329,7 @@ pub async fn fetch_layout(
 pub async fn send_layout(
 	rpc_cli: &Endpoint<SystemRpc, ()>,
 	rpc_host: NodeID,
-	layout: ClusterLayout,
+	layout: LayoutHistory,
 ) -> Result<(), Error> {
 	rpc_cli
 		.call(
@ -327,7 +341,7 @@ pub async fn send_layout(
 	Ok(())
 }
-pub fn print_cluster_layout(layout: &ClusterLayout, empty_msg: &str) {
+pub fn print_cluster_layout(layout: &LayoutVersion, empty_msg: &str) {
 	let mut table = vec!["ID\tTags\tZone\tCapacity\tUsable capacity".to_string()];
 	for (id, _, role) in layout.roles.items().iter() {
 		let role = match &role.0 {
@ -366,21 +380,22 @@ pub fn print_cluster_layout(layout: &ClusterLayout, empty_msg: &str) {
 	}
 }
-pub fn print_staging_role_changes(layout: &ClusterLayout) -> bool {
+pub fn print_staging_role_changes(layout: &LayoutHistory) -> bool {
-	let has_role_changes = layout
+	let staging = layout.staging.get();
-		.staging_roles
+	let has_role_changes = staging
 		.roles
 		.items()
 		.iter()
-		.any(|(k, _, v)| layout.roles.get(k) != Some(v));
+		.any(|(k, _, v)| layout.current().roles.get(k) != Some(v));
-	let has_layout_changes = *layout.staging_parameters.get() != layout.parameters;
+	let has_layout_changes = *staging.parameters.get() != layout.current().parameters;
 	if has_role_changes || has_layout_changes {
 		println!();
 		println!("==== STAGED ROLE CHANGES ====");
 		if has_role_changes {
 			let mut table = vec!["ID\tTags\tZone\tCapacity".to_string()];
-			for (id, _, role) in layout.staging_roles.items().iter() {
+			for (id, _, role) in staging.roles.items().iter() {
-				if layout.roles.get(id) == Some(role) {
+				if layout.current().roles.get(id) == Some(role) {
 					continue;
 				}
 				if let Some(role) = &role.0 {
@ -402,7 +417,7 @@ pub fn print_staging_role_changes(layout: &ClusterLayout) -> bool {
 		if has_layout_changes {
 			println!(
 				"Zone redundancy: {}",
-				layout.staging_parameters.get().zone_redundancy
+				staging.parameters.get().zone_redundancy
 			);
 		}
 		true
--- a/src/garage/cli/structs.rs
+++ b/src/garage/cli/structs.rs
@ -164,9 +164,9 @@ pub struct ApplyLayoutOpt {
 #[derive(StructOpt, Debug)]
 pub struct RevertLayoutOpt {
-	/// Version number of old configuration to which to revert
+	/// The revert operation will not be ran unless this flag is added
-	#[structopt(long = "version")]
+	#[structopt(long = "yes")]
-	pub(crate) version: Option<u64>,
+	pub(crate) yes: bool,
 }
 #[derive(Serialize, Deserialize, StructOpt, Debug)]
--- a/src/garage/tests/common/ext/process.rs
+++ b/src/garage/tests/common/ext/process.rs
@ -14,42 +14,20 @@ impl CommandExt for process::Command {
 	}
 	fn expect_success_status(&mut self, msg: &str) -> process::ExitStatus {
-		let status = self.status().expect(msg);
+		self.expect_success_output(msg).status
 		status.expect_success(msg);
 		status
 	}
 	fn expect_success_output(&mut self, msg: &str) -> process::Output {
 		let output = self.output().expect(msg);
-		output.expect_success(msg);
+		if !output.status.success() {
 			panic!(
 				"{}: command {:?} exited with error {:?}\nSTDOUT: {}\nSTDERR: {}",
 				msg,
 				self,
 				output.status.code(),
 				String::from_utf8_lossy(&output.stdout),
 				String::from_utf8_lossy(&output.stderr)
 			);
 		}
 		output
 	}
 }
 pub trait OutputExt {
 	fn expect_success(&self, msg: &str);
 }
 impl OutputExt for process::Output {
 	fn expect_success(&self, msg: &str) {
 		self.status.expect_success(msg)
 	}
 }
 pub trait ExitStatusExt {
 	fn expect_success(&self, msg: &str);
 }
 impl ExitStatusExt for process::ExitStatus {
 	fn expect_success(&self, msg: &str) {
 		if !self.success() {
 			match self.code() {
 				Some(code) => panic!(
 					"Command exited with code {code}: {msg}",
 					code = code,
 					msg = msg
 				),
 				None => panic!("Command exited with signal: {msg}", msg = msg),
 			}
 		}
 	}
 }
--- a/src/garage/tests/common/garage.rs
+++ b/src/garage/tests/common/garage.rs
@ -96,7 +96,7 @@ api_bind_addr = "127.0.0.1:{admin_port}"
 			.arg("server")
 			.stdout(stdout)
 			.stderr(stderr)
-			.env("RUST_LOG", "garage=info,garage_api=trace")
+			.env("RUST_LOG", "garage=debug,garage_api=trace")
 			.spawn()
 			.expect("Could not start garage");
--- a/src/model/helper/bucket.rs
+++ b/src/model/helper/bucket.rs
@ -450,10 +450,12 @@ impl<'a> BucketHelper<'a> {
 		#[cfg(feature = "k2v")]
 		{
-			use garage_rpc::ring::Ring;
+			let node_id_vec = self
-			use std::sync::Arc;
+				.0
-
+				.system
-			let ring: Arc<Ring> = self.0.system.ring.borrow().clone();
+				.cluster_layout()
 				.all_nongateway_nodes()
 				.to_vec();
 			let k2vindexes = self
 				.0
 				.k2v
@ -462,7 +464,7 @@ impl<'a> BucketHelper<'a> {
 				.get_range(
 					&bucket_id,
 					None,
-					Some((DeletedFilter::NotDeleted, ring.layout.node_id_vec.clone())),
+					Some((DeletedFilter::NotDeleted, node_id_vec)),
 					10,
 					EnumerationOrder::Forward,
 				)
--- a/src/model/index_counter.rs
+++ b/src/model/index_counter.rs
@ -7,7 +7,7 @@ use serde::{Deserialize, Serialize};
 use garage_db as db;
-use garage_rpc::ring::Ring;
+use garage_rpc::layout::LayoutHelper;
 use garage_rpc::system::System;
 use garage_util::background::BackgroundRunner;
 use garage_util::data::*;
@ -83,9 +83,9 @@ impl<T: CountedItem> Entry<T::CP, T::CS> for CounterEntry<T> {
 }
 impl<T: CountedItem> CounterEntry<T> {
-	pub fn filtered_values(&self, ring: &Ring) -> HashMap<String, i64> {
+	pub fn filtered_values(&self, layout: &LayoutHelper) -> HashMap<String, i64> {
-		let nodes = &ring.layout.node_id_vec[..];
+		let nodes = layout.all_nongateway_nodes();
-		self.filtered_values_with_nodes(nodes)
+		self.filtered_values_with_nodes(&nodes)
 	}
 	pub fn filtered_values_with_nodes(&self, nodes: &[Uuid]) -> HashMap<String, i64> {
--- a/src/model/k2v/rpc.rs
+++ b/src/model/k2v/rpc.rs
@ -127,23 +127,21 @@ impl K2VRpcHandler {
 			.item_table
 			.data
 			.replication
-			.write_nodes(&partition.hash());
+			.storage_nodes(&partition.hash());
 		who.sort();
 		self.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
-				&who[..],
+				&who,
 				K2VRpc::InsertItem(InsertedItem {
 					partition,
 					sort_key,
 					causal_context,
 					value,
 				}),
-				RequestStrategy::with_priority(PRIO_NORMAL)
+				RequestStrategy::with_priority(PRIO_NORMAL).with_quorum(1),
 					.with_quorum(1)
 					.interrupt_after_quorum(true),
 			)
 			.await?;
@ -168,7 +166,7 @@ impl K2VRpcHandler {
 				.item_table
 				.data
 				.replication
-				.write_nodes(&partition.hash());
+				.storage_nodes(&partition.hash());
 			who.sort();
 			call_list.entry(who).or_default().push(InsertedItem {
@ -187,14 +185,12 @@ impl K2VRpcHandler {
 		let call_futures = call_list.into_iter().map(|(nodes, items)| async move {
 			let resp = self
 				.system
-				.rpc
+				.rpc_helper()
 				.try_call_many(
 					&self.endpoint,
 					&nodes[..],
 					K2VRpc::InsertManyItems(items),
-					RequestStrategy::with_priority(PRIO_NORMAL)
+					RequestStrategy::with_priority(PRIO_NORMAL).with_quorum(1),
 						.with_quorum(1)
 						.interrupt_after_quorum(true),
 				)
 				.await?;
 			Ok::<_, Error>((nodes, resp))
@ -223,15 +219,16 @@ impl K2VRpcHandler {
 			},
 			sort_key,
 		};
 		// TODO figure this out with write sets, is it still appropriate???
 		let nodes = self
 			.item_table
 			.data
 			.replication
-			.write_nodes(&poll_key.partition.hash());
+			.read_nodes(&poll_key.partition.hash());
-		let rpc = self.system.rpc.try_call_many(
+		let rpc = self.system.rpc_helper().try_call_many(
 			&self.endpoint,
-			&nodes[..],
+			&nodes,
 			K2VRpc::PollItem {
 				key: poll_key,
 				causal_context,
@ -239,9 +236,11 @@ impl K2VRpcHandler {
 			},
 			RequestStrategy::with_priority(PRIO_NORMAL)
 				.with_quorum(self.item_table.data.replication.read_quorum())
 				.send_all_at_once(true)
 				.without_timeout(),
 		);
-		let timeout_duration = Duration::from_millis(timeout_msec) + self.system.rpc.rpc_timeout();
+		let timeout_duration =
 			Duration::from_millis(timeout_msec) + self.system.rpc_helper().rpc_timeout();
 		let resps = select! {
 			r = rpc => r?,
 			_ = tokio::time::sleep(timeout_duration) => return Ok(None),
@ -283,11 +282,12 @@ impl K2VRpcHandler {
 		seen.restrict(&range);
 		// Prepare PollRange RPC to send to the storage nodes responsible for the parititon
 		// TODO figure this out with write sets, does it still work????
 		let nodes = self
 			.item_table
 			.data
 			.replication
-			.write_nodes(&range.partition.hash());
+			.read_nodes(&range.partition.hash());
 		let quorum = self.item_table.data.replication.read_quorum();
 		let msg = K2VRpc::PollRange {
 			range,
@ -300,7 +300,11 @@ impl K2VRpcHandler {
 		let rs = RequestStrategy::with_priority(PRIO_NORMAL).without_timeout();
 		let mut requests = nodes
 			.iter()
-			.map(|node| self.system.rpc.call(&self.endpoint, *node, msg.clone(), rs))
+			.map(|node| {
 				self.system
 					.rpc_helper()
 					.call(&self.endpoint, *node, msg.clone(), rs)
 			})
 			.collect::<FuturesUnordered<_>>();
 		// Fetch responses. This procedure stops fetching responses when any of the following
@ -316,8 +320,9 @@ impl K2VRpcHandler {
 		// kind: all items produced by that node until time ts have been returned, so we can
 		// bump the entry in the global vector clock and possibly remove some item-specific
 		// vector clocks)
-		let mut deadline =
+		let mut deadline = Instant::now()
-			Instant::now() + Duration::from_millis(timeout_msec) + self.system.rpc.rpc_timeout();
+			+ Duration::from_millis(timeout_msec)
 			+ self.system.rpc_helper().rpc_timeout();
 		let mut resps = vec![];
 		let mut errors = vec![];
 		loop {
@ -339,7 +344,7 @@ impl K2VRpcHandler {
 		}
 		if errors.len() > nodes.len() - quorum {
 			let errors = errors.iter().map(|e| format!("{}", e)).collect::<Vec<_>>();
-			return Err(Error::Quorum(quorum, resps.len(), nodes.len(), errors).into());
+			return Err(Error::Quorum(quorum, None, resps.len(), nodes.len(), errors).into());
 		}
 		// Take all returned items into account to produce the response.
--- a/src/rpc/layout/graph_algo.rs
+++ b/src/rpc/layout/graph_algo.rs
@ -114,16 +114,6 @@ impl Graph<FlowEdge> {
 		Ok(result)
 	}
 	/// This function returns the value of the flow incoming to v.
 	pub fn get_inflow(&self, v: Vertex) -> Result<i64, String> {
 		let idv = self.get_vertex_id(&v)?;
 		let mut result = 0;
 		for edge in self.graph[idv].iter() {
 			result += max(0, self.graph[edge.dest][edge.rev].flow);
 		}
 		Ok(result)
 	}
 	/// This function returns the value of the flow outgoing from v.
 	pub fn get_outflow(&self, v: Vertex) -> Result<i64, String> {
 		let idv = self.get_vertex_id(&v)?;
--- a/src/rpc/layout/helper.rs
+++ b/src/rpc/layout/helper.rs
@ -0,0 +1,247 @@
 use std::collections::HashMap;
 use std::ops::Deref;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use serde::{Deserialize, Serialize};
 use garage_util::data::*;
 use super::schema::*;
 #[derive(Debug, Clone, Serialize, Deserialize, Default, PartialEq, Eq)]
 pub struct LayoutDigest {
 	/// Cluster layout version
 	pub current_version: u64,
 	/// Number of active layout versions
 	pub active_versions: usize,
 	/// Hash of cluster layout update trackers
 	pub trackers_hash: Hash,
 	/// Hash of cluster layout staging data
 	pub staging_hash: Hash,
 }
 pub struct LayoutHelper {
 	layout: Option<LayoutHistory>,
 	// cached values
 	ack_map_min: u64,
 	sync_map_min: u64,
 	all_nodes: Vec<Uuid>,
 	all_nongateway_nodes: Vec<Uuid>,
 	trackers_hash: Hash,
 	staging_hash: Hash,
 	// ack lock: counts in-progress write operations for each
 	// layout version ; we don't increase the ack update tracker
 	// while this lock is nonzero
 	pub(crate) ack_lock: HashMap<u64, AtomicUsize>,
 }
 impl Deref for LayoutHelper {
 	type Target = LayoutHistory;
 	fn deref(&self) -> &LayoutHistory {
 		self.layout()
 	}
 }
 impl LayoutHelper {
 	pub fn new(mut layout: LayoutHistory, mut ack_lock: HashMap<u64, AtomicUsize>) -> Self {
 		layout.cleanup_old_versions();
 		let all_nongateway_nodes = layout.get_all_nongateway_nodes();
 		layout.clamp_update_trackers(&all_nongateway_nodes);
 		let min_version = layout.min_stored();
 		let ack_map_min = layout
 			.update_trackers
 			.ack_map
 			.min(&all_nongateway_nodes, min_version);
 		let sync_map_min = layout
 			.update_trackers
 			.sync_map
 			.min(&all_nongateway_nodes, min_version);
 		let all_nodes = layout.get_all_nodes();
 		let trackers_hash = layout.calculate_trackers_hash();
 		let staging_hash = layout.calculate_staging_hash();
 		ack_lock.retain(|_, cnt| *cnt.get_mut() > 0);
 		ack_lock
 			.entry(layout.current().version)
 			.or_insert(AtomicUsize::new(0));
 		LayoutHelper {
 			layout: Some(layout),
 			ack_map_min,
 			sync_map_min,
 			all_nodes,
 			all_nongateway_nodes,
 			trackers_hash,
 			staging_hash,
 			ack_lock,
 		}
 	}
 	// ------------------ single updating function --------------
 	fn layout(&self) -> &LayoutHistory {
 		self.layout.as_ref().unwrap()
 	}
 	pub(crate) fn update<F>(&mut self, f: F) -> bool
 	where
 		F: FnOnce(&mut LayoutHistory) -> bool,
 	{
 		let changed = f(&mut self.layout.as_mut().unwrap());
 		if changed {
 			*self = Self::new(
 				self.layout.take().unwrap(),
 				std::mem::take(&mut self.ack_lock),
 			);
 		}
 		changed
 	}
 	// ------------------ read helpers ---------------
 	pub fn all_nodes(&self) -> &[Uuid] {
 		&self.all_nodes
 	}
 	pub fn all_nongateway_nodes(&self) -> &[Uuid] {
 		&self.all_nongateway_nodes
 	}
 	pub fn all_ack(&self) -> u64 {
 		self.ack_map_min
 	}
 	pub fn sync_versions(&self) -> (u64, u64, u64) {
 		(
 			self.layout().current().version,
 			self.all_ack(),
 			self.layout().min_stored(),
 		)
 	}
 	pub fn read_nodes_of(&self, position: &Hash) -> Vec<Uuid> {
 		let sync_min = self.sync_map_min;
 		let version = self
 			.layout()
 			.versions
 			.iter()
 			.find(|x| x.version == sync_min)
 			.or(self.layout().versions.last())
 			.unwrap();
 		version
 			.nodes_of(position, version.replication_factor)
 			.collect()
 	}
 	pub(crate) fn write_sets_of(&self, position: &Hash) -> Vec<Vec<Uuid>> {
 		self.layout()
 			.versions
 			.iter()
 			.map(|x| x.nodes_of(position, x.replication_factor).collect())
 			.collect()
 	}
 	pub fn storage_nodes_of(&self, position: &Hash) -> Vec<Uuid> {
 		let mut ret = vec![];
 		for version in self.layout().versions.iter() {
 			ret.extend(version.nodes_of(position, version.replication_factor));
 		}
 		ret.sort();
 		ret.dedup();
 		ret
 	}
 	pub fn trackers_hash(&self) -> Hash {
 		self.trackers_hash
 	}
 	pub fn staging_hash(&self) -> Hash {
 		self.staging_hash
 	}
 	pub fn digest(&self) -> LayoutDigest {
 		LayoutDigest {
 			current_version: self.current().version,
 			active_versions: self.versions.len(),
 			trackers_hash: self.trackers_hash,
 			staging_hash: self.staging_hash,
 		}
 	}
 	// ------------------ helpers for update tracking ---------------
 	pub(crate) fn update_trackers(&mut self, local_node_id: Uuid) {
 		// Ensure trackers for this node's values are up-to-date
 		// 1. Acknowledge the last layout version which is not currently
 		//    locked by an in-progress write operation
 		self.ack_max_free(local_node_id);
 		// 2. Assume the data on this node is sync'ed up at least to
 		//    the first layout version in the history
 		self.sync_first(local_node_id);
 		// 3. Acknowledge everyone has synced up to min(self.sync_map)
 		self.sync_ack(local_node_id);
 		info!("ack_map: {:?}", self.update_trackers.ack_map);
 		info!("sync_map: {:?}", self.update_trackers.sync_map);
 		info!("sync_ack_map: {:?}", self.update_trackers.sync_ack_map);
 	}
 	fn sync_first(&mut self, local_node_id: Uuid) {
 		let first_version = self.versions.first().as_ref().unwrap().version;
 		self.update(|layout| {
 			layout
 				.update_trackers
 				.sync_map
 				.set_max(local_node_id, first_version)
 		});
 	}
 	fn sync_ack(&mut self, local_node_id: Uuid) {
 		let sync_map_min = self.sync_map_min;
 		self.update(|layout| {
 			layout
 				.update_trackers
 				.sync_ack_map
 				.set_max(local_node_id, sync_map_min)
 		});
 	}
 	pub(crate) fn ack_max_free(&mut self, local_node_id: Uuid) -> bool {
 		let max_ack = self.max_free_ack();
 		let changed = self.update(|layout| {
 			layout
 				.update_trackers
 				.ack_map
 				.set_max(local_node_id, max_ack)
 		});
 		if changed {
 			info!("ack_until updated to {}", max_ack);
 		}
 		changed
 	}
 	pub(crate) fn max_free_ack(&self) -> u64 {
 		self.layout()
 			.versions
 			.iter()
 			.map(|x| x.version)
 			.take_while(|v| {
 				self.ack_lock
 					.get(v)
 					.map(|x| x.load(Ordering::Relaxed) == 0)
 					.unwrap_or(true)
 			})
 			.max()
 			.unwrap_or(self.min_stored())
 	}
 }
--- a/src/rpc/layout/history.rs
+++ b/src/rpc/layout/history.rs
@ -0,0 +1,198 @@
 use std::collections::HashSet;
 use garage_util::crdt::{Crdt, Lww, LwwMap};
 use garage_util::data::*;
 use garage_util::encode::nonversioned_encode;
 use garage_util::error::*;
 use super::*;
 impl LayoutHistory {
 	pub fn new(replication_factor: usize) -> Self {
 		let version = LayoutVersion::new(replication_factor);
 		let staging = LayoutStaging {
 			parameters: Lww::<LayoutParameters>::new(version.parameters),
 			roles: LwwMap::new(),
 		};
 		LayoutHistory {
 			versions: vec![version],
 			update_trackers: Default::default(),
 			staging: Lww::raw(0, staging),
 		}
 	}
 	// ------------------ who stores what now? ---------------
 	pub fn current(&self) -> &LayoutVersion {
 		self.versions.last().as_ref().unwrap()
 	}
 	pub fn min_stored(&self) -> u64 {
 		self.versions.first().as_ref().unwrap().version
 	}
 	pub fn get_all_nodes(&self) -> Vec<Uuid> {
 		if self.versions.len() == 1 {
 			self.versions[0].all_nodes().to_vec()
 		} else {
 			let set = self
 				.versions
 				.iter()
 				.map(|x| x.all_nodes())
 				.flatten()
 				.collect::<HashSet<_>>();
 			set.into_iter().copied().collect::<Vec<_>>()
 		}
 	}
 	pub(crate) fn get_all_nongateway_nodes(&self) -> Vec<Uuid> {
 		if self.versions.len() == 1 {
 			self.versions[0].nongateway_nodes().to_vec()
 		} else {
 			let set = self
 				.versions
 				.iter()
 				.map(|x| x.nongateway_nodes())
 				.flatten()
 				.collect::<HashSet<_>>();
 			set.into_iter().copied().collect::<Vec<_>>()
 		}
 	}
 	// ---- housekeeping (all invoked by LayoutHelper) ----
 	pub(crate) fn cleanup_old_versions(&mut self) {
 		// If there are invalid versions before valid versions, remove them
 		if self.versions.len() > 1 && self.current().check().is_ok() {
 			while self.versions.len() > 1 && self.versions.first().unwrap().check().is_err() {
 				let removed = self.versions.remove(0);
 				info!(
 					"Layout history: pruning old invalid version {}",
 					removed.version
 				);
 			}
 		}
 		// If there are old versions that no one is reading from anymore,
 		// remove them
 		while self.versions.len() > 1 {
 			let all_nongateway_nodes = self.get_all_nongateway_nodes();
 			let min_version = self.min_stored();
 			let sync_ack_map_min = self
 				.update_trackers
 				.sync_ack_map
 				.min(&all_nongateway_nodes, min_version);
 			if self.min_stored() < sync_ack_map_min {
 				let removed = self.versions.remove(0);
 				info!("Layout history: pruning old version {}", removed.version);
 			} else {
 				break;
 			}
 		}
 	}
 	pub(crate) fn clamp_update_trackers(&mut self, nodes: &[Uuid]) {
 		let min_v = self.min_stored();
 		for node in nodes {
 			self.update_trackers.ack_map.set_max(*node, min_v);
 			self.update_trackers.sync_map.set_max(*node, min_v);
 			self.update_trackers.sync_ack_map.set_max(*node, min_v);
 		}
 	}
 	pub(crate) fn calculate_trackers_hash(&self) -> Hash {
 		blake2sum(&nonversioned_encode(&self.update_trackers).unwrap()[..])
 	}
 	pub(crate) fn calculate_staging_hash(&self) -> Hash {
 		blake2sum(&nonversioned_encode(&self.staging).unwrap()[..])
 	}
 	// ================== updates to layout, public interface ===================
 	pub fn merge(&mut self, other: &LayoutHistory) -> bool {
 		let mut changed = false;
 		// Add any new versions to history
 		for v2 in other.versions.iter() {
 			if let Some(v1) = self.versions.iter().find(|v| v.version == v2.version) {
 				// Version is already present, check consistency
 				if v1 != v2 {
 					error!("Inconsistent layout histories: different layout compositions for version {}. Your cluster will be broken as long as this layout version is not replaced.", v2.version);
 				}
 			} else if self.versions.iter().all(|v| v.version != v2.version - 1) {
 				error!(
 					"Cannot receive new layout version {}, version {} is missing",
 					v2.version,
 					v2.version - 1
 				);
 			} else {
 				self.versions.push(v2.clone());
 				changed = true;
 			}
 		}
 		// Merge trackers
 		let c = self.update_trackers.merge(&other.update_trackers);
 		changed = changed || c;
 		// Merge staged layout changes
 		if self.staging != other.staging {
 			let prev_staging = self.staging.clone();
 			self.staging.merge(&other.staging);
 			changed = changed || self.staging != prev_staging;
 		}
 		changed
 	}
 	pub fn apply_staged_changes(mut self, version: Option<u64>) -> Result<(Self, Message), Error> {
 		match version {
 			None => {
 				let error = r#"
 Please pass the new layout version number to ensure that you are writing the correct version of the cluster layout.
 To know the correct value of the new layout version, invoke `garage layout show` and review the proposed changes.
 				"#;
 				return Err(Error::Message(error.into()));
 			}
 			Some(v) => {
 				if v != self.current().version + 1 {
 					return Err(Error::Message("Invalid new layout version".into()));
 				}
 			}
 		}
 		// Compute new version and add it to history
 		let (new_version, msg) = self
 			.current()
 			.clone()
 			.calculate_next_version(&self.staging.get())?;
 		self.versions.push(new_version);
 		self.cleanup_old_versions();
 		// Reset the staged layout changes
 		self.staging.update(LayoutStaging {
 			parameters: self.staging.get().parameters.clone(),
 			roles: LwwMap::new(),
 		});
 		Ok((self, msg))
 	}
 	pub fn revert_staged_changes(mut self) -> Result<Self, Error> {
 		self.staging.update(LayoutStaging {
 			parameters: Lww::new(self.current().parameters.clone()),
 			roles: LwwMap::new(),
 		});
 		Ok(self)
 	}
 	pub fn check(&self) -> Result<(), String> {
 		// TODO: anything more ?
 		self.current().check()
 	}
 }
--- a/src/rpc/layout/manager.rs
+++ b/src/rpc/layout/manager.rs
@ -0,0 +1,368 @@
 use std::collections::HashMap;
 use std::sync::{atomic::Ordering, Arc, Mutex, RwLock, RwLockReadGuard};
 use std::time::Duration;
 use tokio::sync::Notify;
 use netapp::endpoint::Endpoint;
 use netapp::peering::fullmesh::FullMeshPeeringStrategy;
 use netapp::NodeID;
 use garage_util::config::Config;
 use garage_util::data::*;
 use garage_util::error::*;
 use garage_util::persister::Persister;
 use super::*;
 use crate::rpc_helper::*;
 use crate::system::*;
 pub struct LayoutManager {
 	node_id: Uuid,
 	replication_factor: usize,
 	persist_cluster_layout: Persister<LayoutHistory>,
 	layout: Arc<RwLock<LayoutHelper>>,
 	pub(crate) change_notify: Arc<Notify>,
 	table_sync_version: Mutex<HashMap<String, u64>>,
 	pub(crate) rpc_helper: RpcHelper,
 	system_endpoint: Arc<Endpoint<SystemRpc, System>>,
 }
 impl LayoutManager {
 	pub fn new(
 		config: &Config,
 		node_id: NodeID,
 		system_endpoint: Arc<Endpoint<SystemRpc, System>>,
 		fullmesh: Arc<FullMeshPeeringStrategy>,
 		replication_factor: usize,
 	) -> Result<Arc<Self>, Error> {
 		let persist_cluster_layout: Persister<LayoutHistory> =
 			Persister::new(&config.metadata_dir, "cluster_layout");
 		let cluster_layout = match persist_cluster_layout.load() {
 			Ok(x) => {
 				if x.current().replication_factor != replication_factor {
 					return Err(Error::Message(format!(
 						"Prevous cluster layout has replication factor {}, which is different than the one specified in the config file ({}). The previous cluster layout can be purged, if you know what you are doing, simply by deleting the `cluster_layout` file in your metadata directory.",
 						x.current().replication_factor,
 						replication_factor
 					)));
 				}
 				x
 			}
 			Err(e) => {
 				info!(
 					"No valid previous cluster layout stored ({}), starting fresh.",
 					e
 				);
 				LayoutHistory::new(replication_factor)
 			}
 		};
 		let mut cluster_layout = LayoutHelper::new(cluster_layout, Default::default());
 		cluster_layout.update_trackers(node_id.into());
 		let layout = Arc::new(RwLock::new(cluster_layout));
 		let change_notify = Arc::new(Notify::new());
 		let rpc_helper = RpcHelper::new(
 			node_id.into(),
 			fullmesh,
 			layout.clone(),
 			config.rpc_timeout_msec.map(Duration::from_millis),
 		);
 		Ok(Arc::new(Self {
 			node_id: node_id.into(),
 			replication_factor,
 			persist_cluster_layout,
 			layout,
 			change_notify,
 			table_sync_version: Mutex::new(HashMap::new()),
 			system_endpoint,
 			rpc_helper,
 		}))
 	}
 	// ---- PUBLIC INTERFACE ----
 	pub fn layout(&self) -> RwLockReadGuard<'_, LayoutHelper> {
 		self.layout.read().unwrap()
 	}
 	pub async fn update_cluster_layout(
 		self: &Arc<Self>,
 		layout: &LayoutHistory,
 	) -> Result<(), Error> {
 		self.handle_advertise_cluster_layout(layout).await?;
 		Ok(())
 	}
 	pub fn add_table(&self, table_name: &'static str) {
 		let first_version = self.layout().versions.first().unwrap().version;
 		self.table_sync_version
 			.lock()
 			.unwrap()
 			.insert(table_name.to_string(), first_version);
 	}
 	pub fn sync_table_until(self: &Arc<Self>, table_name: &'static str, version: u64) {
 		let mut table_sync_version = self.table_sync_version.lock().unwrap();
 		*table_sync_version.get_mut(table_name).unwrap() = version;
 		let sync_until = table_sync_version.iter().map(|(_, v)| *v).min().unwrap();
 		drop(table_sync_version);
 		let mut layout = self.layout.write().unwrap();
 		if layout.update(|l| l.update_trackers.sync_map.set_max(self.node_id, sync_until)) {
 			info!("sync_until updated to {}", sync_until);
 			self.broadcast_update(SystemRpc::AdvertiseClusterLayoutTrackers(
 				layout.update_trackers.clone(),
 			));
 		}
 	}
 	fn ack_new_version(self: &Arc<Self>) {
 		let mut layout = self.layout.write().unwrap();
 		if layout.ack_max_free(self.node_id) {
 			self.broadcast_update(SystemRpc::AdvertiseClusterLayoutTrackers(
 				layout.update_trackers.clone(),
 			));
 		}
 	}
 	// ---- ACK LOCKING ----
 	pub fn write_sets_of(self: &Arc<Self>, position: &Hash) -> WriteLock<Vec<Vec<Uuid>>> {
 		let layout = self.layout();
 		let version = layout.current().version;
 		let nodes = layout.write_sets_of(position);
 		layout
 			.ack_lock
 			.get(&version)
 			.unwrap()
 			.fetch_add(1, Ordering::Relaxed);
 		WriteLock::new(version, self, nodes)
 	}
 	// ---- INTERNALS ---
 	fn merge_layout(&self, adv: &LayoutHistory) -> Option<LayoutHistory> {
 		let mut layout = self.layout.write().unwrap();
 		let prev_digest = layout.digest();
 		let prev_layout_check = layout.check().is_ok();
 		if !prev_layout_check || adv.check().is_ok() {
 			if layout.update(|l| l.merge(adv)) {
 				layout.update_trackers(self.node_id);
 				if prev_layout_check && layout.check().is_err() {
 					panic!("Merged two correct layouts and got an incorrect layout.");
 				}
 				assert!(layout.digest() != prev_digest);
 				return Some(layout.clone());
 			}
 		}
 		None
 	}
 	fn merge_layout_trackers(&self, adv: &UpdateTrackers) -> Option<UpdateTrackers> {
 		let mut layout = self.layout.write().unwrap();
 		let prev_digest = layout.digest();
 		if layout.update_trackers != *adv {
 			if layout.update(|l| l.update_trackers.merge(adv)) {
 				layout.update_trackers(self.node_id);
 				assert!(layout.digest() != prev_digest);
 				return Some(layout.update_trackers.clone());
 			}
 		}
 		None
 	}
 	async fn pull_cluster_layout(self: &Arc<Self>, peer: Uuid) {
 		let resp = self
 			.rpc_helper
 			.call(
 				&self.system_endpoint,
 				peer,
 				SystemRpc::PullClusterLayout,
 				RequestStrategy::with_priority(PRIO_HIGH),
 			)
 			.await;
 		if let Ok(SystemRpc::AdvertiseClusterLayout(layout)) = resp {
 			if let Err(e) = self.handle_advertise_cluster_layout(&layout).await {
 				warn!("In pull_cluster_layout: {}", e);
 			}
 		}
 	}
 	async fn pull_cluster_layout_trackers(self: &Arc<Self>, peer: Uuid) {
 		let resp = self
 			.rpc_helper
 			.call(
 				&self.system_endpoint,
 				peer,
 				SystemRpc::PullClusterLayoutTrackers,
 				RequestStrategy::with_priority(PRIO_HIGH),
 			)
 			.await;
 		if let Ok(SystemRpc::AdvertiseClusterLayoutTrackers(trackers)) = resp {
 			if let Err(e) = self
 				.handle_advertise_cluster_layout_trackers(&trackers)
 				.await
 			{
 				warn!("In pull_cluster_layout_trackers: {}", e);
 			}
 		}
 	}
 	/// Save cluster layout data to disk
 	async fn save_cluster_layout(&self) -> Result<(), Error> {
 		let layout = self.layout.read().unwrap().clone();
 		self.persist_cluster_layout
 			.save_async(&layout)
 			.await
 			.expect("Cannot save current cluster layout");
 		Ok(())
 	}
 	fn broadcast_update(self: &Arc<Self>, rpc: SystemRpc) {
 		tokio::spawn({
 			let this = self.clone();
 			async move {
 				if let Err(e) = this
 					.rpc_helper
 					.broadcast(
 						&this.system_endpoint,
 						rpc,
 						RequestStrategy::with_priority(PRIO_HIGH),
 					)
 					.await
 				{
 					warn!("Error while broadcasting new cluster layout: {}", e);
 				}
 			}
 		});
 	}
 	// ---- RPC HANDLERS ----
 	pub(crate) fn handle_advertise_status(self: &Arc<Self>, from: Uuid, remote: &LayoutDigest) {
 		let local = self.layout().digest();
 		if remote.current_version > local.current_version
 			|| remote.active_versions != local.active_versions
 			|| remote.staging_hash != local.staging_hash
 		{
 			tokio::spawn({
 				let this = self.clone();
 				async move { this.pull_cluster_layout(from).await }
 			});
 		} else if remote.trackers_hash != local.trackers_hash {
 			tokio::spawn({
 				let this = self.clone();
 				async move { this.pull_cluster_layout_trackers(from).await }
 			});
 		}
 	}
 	pub(crate) fn handle_pull_cluster_layout(&self) -> SystemRpc {
 		let layout = self.layout.read().unwrap().clone();
 		SystemRpc::AdvertiseClusterLayout(layout)
 	}
 	pub(crate) fn handle_pull_cluster_layout_trackers(&self) -> SystemRpc {
 		let layout = self.layout.read().unwrap();
 		SystemRpc::AdvertiseClusterLayoutTrackers(layout.update_trackers.clone())
 	}
 	pub(crate) async fn handle_advertise_cluster_layout(
 		self: &Arc<Self>,
 		adv: &LayoutHistory,
 	) -> Result<SystemRpc, Error> {
 		debug!(
 			"handle_advertise_cluster_layout: {} versions, last={}, trackers={:?}",
 			adv.versions.len(),
 			adv.current().version,
 			adv.update_trackers
 		);
 		if adv.current().replication_factor != self.replication_factor {
 			let msg = format!(
 				"Received a cluster layout from another node with replication factor {}, which is different from what we have in our configuration ({}). Discarding the cluster layout we received.",
 				adv.current().replication_factor,
 				self.replication_factor
 			);
 			error!("{}", msg);
 			return Err(Error::Message(msg));
 		}
 		if let Some(new_layout) = self.merge_layout(adv) {
 			debug!("handle_advertise_cluster_layout: some changes were added to the current stuff");
 			self.change_notify.notify_waiters();
 			self.broadcast_update(SystemRpc::AdvertiseClusterLayout(new_layout));
 			self.save_cluster_layout().await?;
 		}
 		Ok(SystemRpc::Ok)
 	}
 	pub(crate) async fn handle_advertise_cluster_layout_trackers(
 		self: &Arc<Self>,
 		trackers: &UpdateTrackers,
 	) -> Result<SystemRpc, Error> {
 		debug!("handle_advertise_cluster_layout_trackers: {:?}", trackers);
 		if let Some(new_trackers) = self.merge_layout_trackers(trackers) {
 			self.change_notify.notify_waiters();
 			self.broadcast_update(SystemRpc::AdvertiseClusterLayoutTrackers(new_trackers));
 			self.save_cluster_layout().await?;
 		}
 		Ok(SystemRpc::Ok)
 	}
 }
 // ---- ack lock ----
 pub struct WriteLock<T> {
 	layout_version: u64,
 	layout_manager: Arc<LayoutManager>,
 	value: T,
 }
 impl<T> WriteLock<T> {
 	fn new(version: u64, layout_manager: &Arc<LayoutManager>, value: T) -> Self {
 		Self {
 			layout_version: version,
 			layout_manager: layout_manager.clone(),
 			value,
 		}
 	}
 }
 impl<T> AsRef<T> for WriteLock<T> {
 	fn as_ref(&self) -> &T {
 		&self.value
 	}
 }
 impl<T> Drop for WriteLock<T> {
 	fn drop(&mut self) {
 		let layout = self.layout_manager.layout(); // acquire read lock
 		if let Some(counter) = layout.ack_lock.get(&self.layout_version) {
 			let prev_lock = counter.fetch_sub(1, Ordering::Relaxed);
 			if prev_lock == 1 && layout.current().version > self.layout_version {
 				drop(layout); // release read lock, write lock will be acquired
 				self.layout_manager.ack_new_version();
 			}
 		} else {
 			error!("Could not find ack lock counter for layout version {}. This probably indicates a bug in Garage.", self.layout_version);
 		}
 	}
 }
--- a/src/rpc/layout/mod.rs
+++ b/src/rpc/layout/mod.rs
@ -0,0 +1,41 @@
 mod graph_algo;
 mod helper;
 mod history;
 mod schema;
 mod version;
 #[cfg(test)]
 mod test;
 pub mod manager;
 // ---- re-exports ----
 pub use helper::{LayoutDigest, LayoutHelper};
 pub use manager::WriteLock;
 pub use schema::*;
 pub use version::*;
 // ---- defines: partitions ----
 /// A partition id, which is stored on 16 bits
 /// i.e. we have up to 2**16 partitions.
 /// (in practice we have exactly 2**PARTITION_BITS partitions)
 pub type Partition = u16;
 // TODO: make this constant parametrizable in the config file
 // For deployments with many nodes it might make sense to bump
 // it up to 10.
 // Maximum value : 16
 /// How many bits from the hash are used to make partitions. Higher numbers means more fairness in
 /// presence of numerous nodes, but exponentially bigger ring. Max 16
 pub const PARTITION_BITS: usize = 8;
 const NB_PARTITIONS: usize = 1usize << PARTITION_BITS;
 // ---- defines: nodes ----
 // Type to store compactly the id of a node in the system
 // Change this to u16 the day we want to have more than 256 nodes in a cluster
 pub type CompactNodeType = u8;
 pub const MAX_NODE_NUMBER: usize = 256;
--- a/src/rpc/layout/schema.rs
+++ b/src/rpc/layout/schema.rs
@ -0,0 +1,417 @@
 use std::fmt;
 use bytesize::ByteSize;
 use garage_util::crdt::{AutoCrdt, Crdt};
 use garage_util::data::Uuid;
 mod v08 {
 	use crate::layout::CompactNodeType;
 	use garage_util::crdt::LwwMap;
 	use garage_util::data::{Hash, Uuid};
 	use serde::{Deserialize, Serialize};
 	/// The layout of the cluster, i.e. the list of roles
 	/// which are assigned to each cluster node
 	#[derive(Clone, Debug, Serialize, Deserialize)]
 	pub struct ClusterLayout {
 		pub version: u64,
 		pub replication_factor: usize,
 		pub roles: LwwMap<Uuid, NodeRoleV>,
 		/// node_id_vec: a vector of node IDs with a role assigned
 		/// in the system (this includes gateway nodes).
 		/// The order here is different than the vec stored by `roles`, because:
 		/// 1. non-gateway nodes are first so that they have lower numbers
 		/// 2. nodes that don't have a role are excluded (but they need to
 		///    stay in the CRDT as tombstones)
 		pub node_id_vec: Vec<Uuid>,
 		/// the assignation of data partitions to node, the values
 		/// are indices in node_id_vec
 		#[serde(with = "serde_bytes")]
 		pub ring_assignation_data: Vec<CompactNodeType>,
 		/// Role changes which are staged for the next version of the layout
 		pub staging: LwwMap<Uuid, NodeRoleV>,
 		pub staging_hash: Hash,
 	}
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
 	pub struct NodeRoleV(pub Option<NodeRole>);
 	/// The user-assigned roles of cluster nodes
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
 	pub struct NodeRole {
 		/// Datacenter at which this entry belong. This information is used to
 		/// perform a better geodistribution
 		pub zone: String,
 		/// The capacity of the node
 		/// If this is set to None, the node does not participate in storing data for the system
 		/// and is only active as an API gateway to other nodes
 		pub capacity: Option<u64>,
 		/// A set of tags to recognize the node
 		pub tags: Vec<String>,
 	}
 	impl garage_util::migrate::InitialFormat for ClusterLayout {}
 }
 mod v09 {
 	use super::v08;
 	use crate::layout::CompactNodeType;
 	use garage_util::crdt::{Lww, LwwMap};
 	use garage_util::data::{Hash, Uuid};
 	use serde::{Deserialize, Serialize};
 	pub use v08::{NodeRole, NodeRoleV};
 	/// The layout of the cluster, i.e. the list of roles
 	/// which are assigned to each cluster node
 	#[derive(Clone, Debug, Serialize, Deserialize)]
 	pub struct ClusterLayout {
 		pub version: u64,
 		pub replication_factor: usize,
 		/// This attribute is only used to retain the previously computed partition size,
 		/// to know to what extent does it change with the layout update.
 		pub partition_size: u64,
 		/// Parameters used to compute the assignment currently given by
 		/// ring_assignment_data
 		pub parameters: LayoutParameters,
 		pub roles: LwwMap<Uuid, NodeRoleV>,
 		/// see comment in v08::ClusterLayout
 		pub node_id_vec: Vec<Uuid>,
 		/// see comment in v08::ClusterLayout
 		#[serde(with = "serde_bytes")]
 		pub ring_assignment_data: Vec<CompactNodeType>,
 		/// Parameters to be used in the next partition assignment computation.
 		pub staging_parameters: Lww<LayoutParameters>,
 		/// Role changes which are staged for the next version of the layout
 		pub staging_roles: LwwMap<Uuid, NodeRoleV>,
 		pub staging_hash: Hash,
 	}
 	/// This struct is used to set the parameters to be used in the assignment computation
 	/// algorithm. It is stored as a Crdt.
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug, Serialize, Deserialize)]
 	pub struct LayoutParameters {
 		pub zone_redundancy: ZoneRedundancy,
 	}
 	/// Zone redundancy: if set to AtLeast(x), the layout calculation will aim to store copies
 	/// of each partition on at least that number of different zones.
 	/// Otherwise, copies will be stored on the maximum possible number of zones.
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug, Serialize, Deserialize)]
 	pub enum ZoneRedundancy {
 		AtLeast(usize),
 		Maximum,
 	}
 	impl garage_util::migrate::Migrate for ClusterLayout {
 		const VERSION_MARKER: &'static [u8] = b"G09layout";
 		type Previous = v08::ClusterLayout;
 		fn migrate(previous: Self::Previous) -> Self {
 			use itertools::Itertools;
 			// In the old layout, capacities are in an arbitrary unit,
 			// but in the new layout they are in bytes.
 			// Here we arbitrarily multiply everything by 1G,
 			// such that 1 old capacity unit = 1GB in the new units.
 			// This is totally arbitrary and won't work for most users.
 			let cap_mul = 1024 * 1024 * 1024;
 			let roles = multiply_all_capacities(previous.roles, cap_mul);
 			let staging_roles = multiply_all_capacities(previous.staging, cap_mul);
 			let node_id_vec = previous.node_id_vec;
 			// Determine partition size
 			let mut tmp = previous.ring_assignation_data.clone();
 			tmp.sort();
 			let partition_size = tmp
 				.into_iter()
 				.dedup_with_count()
 				.map(|(npart, node)| {
 					roles
 						.get(&node_id_vec[node as usize])
 						.and_then(|p| p.0.as_ref().and_then(|r| r.capacity))
 						.unwrap_or(0) / npart as u64
 				})
 				.min()
 				.unwrap_or(0);
 			// By default, zone_redundancy is maximum possible value
 			let parameters = LayoutParameters {
 				zone_redundancy: ZoneRedundancy::Maximum,
 			};
 			Self {
 				version: previous.version,
 				replication_factor: previous.replication_factor,
 				partition_size,
 				parameters,
 				roles,
 				node_id_vec,
 				ring_assignment_data: previous.ring_assignation_data,
 				staging_parameters: Lww::new(parameters),
 				staging_roles,
 				staging_hash: [0u8; 32].into(), // will be set in the next migration
 			}
 		}
 	}
 	fn multiply_all_capacities(
 		old_roles: LwwMap<Uuid, NodeRoleV>,
 		mul: u64,
 	) -> LwwMap<Uuid, NodeRoleV> {
 		let mut new_roles = LwwMap::new();
 		for (node, ts, role) in old_roles.items() {
 			let mut role = role.clone();
 			if let NodeRoleV(Some(NodeRole {
 				capacity: Some(ref mut cap),
 				..
 			})) = role
 			{
 				*cap *= mul;
 			}
 			new_roles.merge_raw(node, *ts, &role);
 		}
 		new_roles
 	}
 }
 mod v010 {
 	use super::v09;
 	use crate::layout::CompactNodeType;
 	use garage_util::crdt::{Lww, LwwMap};
 	use garage_util::data::Uuid;
 	use serde::{Deserialize, Serialize};
 	use std::collections::BTreeMap;
 	pub use v09::{LayoutParameters, NodeRole, NodeRoleV, ZoneRedundancy};
 	/// The history of cluster layouts, with trackers to keep a record
 	/// of which nodes are up-to-date to current cluster data
 	#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
 	pub struct LayoutHistory {
 		/// The versions currently in use in the cluster
 		pub versions: Vec<LayoutVersion>,
 		/// Update trackers
 		pub update_trackers: UpdateTrackers,
 		/// Staged changes for the next version
 		pub staging: Lww<LayoutStaging>,
 	}
 	/// A version of the layout of the cluster, i.e. the list of roles
 	/// which are assigned to each cluster node
 	#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
 	pub struct LayoutVersion {
 		pub version: u64,
 		pub replication_factor: usize,
 		/// This attribute is only used to retain the previously computed partition size,
 		/// to know to what extent does it change with the layout update.
 		pub partition_size: u64,
 		/// Parameters used to compute the assignment currently given by
 		/// ring_assignment_data
 		pub parameters: LayoutParameters,
 		pub roles: LwwMap<Uuid, NodeRoleV>,
 		/// see comment in v08::ClusterLayout
 		pub node_id_vec: Vec<Uuid>,
 		/// number of non-gateway nodes, which are the first ids in node_id_vec
 		pub nongateway_node_count: usize,
 		/// see comment in v08::ClusterLayout
 		#[serde(with = "serde_bytes")]
 		pub ring_assignment_data: Vec<CompactNodeType>,
 	}
 	/// The staged changes for the next layout version
 	#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
 	pub struct LayoutStaging {
 		/// Parameters to be used in the next partition assignment computation.
 		pub parameters: Lww<LayoutParameters>,
 		/// Role changes which are staged for the next version of the layout
 		pub roles: LwwMap<Uuid, NodeRoleV>,
 	}
 	/// The tracker of acknowlegments and data syncs around the cluster
 	#[derive(Clone, Debug, Serialize, Deserialize, Default, PartialEq)]
 	pub struct UpdateTrackers {
 		/// The highest layout version number each node has ack'ed
 		pub ack_map: UpdateTracker,
 		/// The highest layout version number each node has synced data for
 		pub sync_map: UpdateTracker,
 		/// The highest layout version number each node has
 		/// ack'ed that all other nodes have synced data for
 		pub sync_ack_map: UpdateTracker,
 	}
 	/// The history of cluster layouts
 	#[derive(Clone, Debug, Serialize, Deserialize, Default, PartialEq)]
 	pub struct UpdateTracker(pub BTreeMap<Uuid, u64>);
 	impl garage_util::migrate::Migrate for LayoutHistory {
 		const VERSION_MARKER: &'static [u8] = b"G010lh";
 		type Previous = v09::ClusterLayout;
 		fn migrate(previous: Self::Previous) -> Self {
 			let nongateway_node_count = previous
 				.node_id_vec
 				.iter()
 				.enumerate()
 				.filter(|(_, uuid)| {
 					let role = previous.roles.get(uuid);
 					matches!(role, Some(NodeRoleV(Some(role))) if role.capacity.is_some())
 				})
 				.map(|(i, _)| i + 1)
 				.max()
 				.unwrap_or(0);
 			let version = LayoutVersion {
 				version: previous.version,
 				replication_factor: previous.replication_factor,
 				partition_size: previous.partition_size,
 				parameters: previous.parameters,
 				roles: previous.roles,
 				node_id_vec: previous.node_id_vec,
 				nongateway_node_count,
 				ring_assignment_data: previous.ring_assignment_data,
 			};
 			let update_tracker = UpdateTracker(
 				version
 					.nongateway_nodes()
 					.iter()
 					.copied()
 					.map(|x| (x, version.version))
 					.collect::<BTreeMap<Uuid, u64>>(),
 			);
 			let staging = LayoutStaging {
 				parameters: previous.staging_parameters,
 				roles: previous.staging_roles,
 			};
 			Self {
 				versions: vec![version],
 				update_trackers: UpdateTrackers {
 					ack_map: update_tracker.clone(),
 					sync_map: update_tracker.clone(),
 					sync_ack_map: update_tracker.clone(),
 				},
 				staging: Lww::raw(previous.version, staging),
 			}
 		}
 	}
 }
 pub use v010::*;
 // ---- utility functions ----
 impl AutoCrdt for LayoutParameters {
 	const WARN_IF_DIFFERENT: bool = true;
 }
 impl AutoCrdt for NodeRoleV {
 	const WARN_IF_DIFFERENT: bool = true;
 }
 impl Crdt for LayoutStaging {
 	fn merge(&mut self, other: &LayoutStaging) {
 		self.parameters.merge(&other.parameters);
 		self.roles.merge(&other.roles);
 	}
 }
 impl NodeRole {
 	pub fn capacity_string(&self) -> String {
 		match self.capacity {
 			Some(c) => ByteSize::b(c).to_string_as(false),
 			None => "gateway".to_string(),
 		}
 	}
 	pub fn tags_string(&self) -> String {
 		self.tags.join(",")
 	}
 }
 impl fmt::Display for ZoneRedundancy {
 	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 		match self {
 			ZoneRedundancy::Maximum => write!(f, "maximum"),
 			ZoneRedundancy::AtLeast(x) => write!(f, "{}", x),
 		}
 	}
 }
 impl core::str::FromStr for ZoneRedundancy {
 	type Err = &'static str;
 	fn from_str(s: &str) -> Result<Self, Self::Err> {
 		match s {
 			"none" | "max" | "maximum" => Ok(ZoneRedundancy::Maximum),
 			x => {
 				let v = x
 					.parse::<usize>()
 					.map_err(|_| "zone redundancy must be 'none'/'max' or an integer")?;
 				Ok(ZoneRedundancy::AtLeast(v))
 			}
 		}
 	}
 }
 impl UpdateTracker {
 	fn merge(&mut self, other: &UpdateTracker) -> bool {
 		let mut changed = false;
 		for (k, v) in other.0.iter() {
 			if let Some(v_mut) = self.0.get_mut(k) {
 				if *v > *v_mut {
 					*v_mut = *v;
 					changed = true;
 				}
 			} else {
 				self.0.insert(*k, *v);
 				changed = true;
 			}
 		}
 		changed
 	}
 	pub(crate) fn set_max(&mut self, peer: Uuid, value: u64) -> bool {
 		match self.0.get_mut(&peer) {
 			Some(e) if *e < value => {
 				*e = value;
 				true
 			}
 			None => {
 				self.0.insert(peer, value);
 				true
 			}
 			_ => false,
 		}
 	}
 	pub(crate) fn min(&self, storage_nodes: &[Uuid], min_version: u64) -> u64 {
 		storage_nodes
 			.iter()
 			.map(|x| self.0.get(x).copied().unwrap_or(min_version))
 			.min()
 			.unwrap_or(min_version)
 	}
 }
 impl UpdateTrackers {
 	pub(crate) fn merge(&mut self, other: &UpdateTrackers) -> bool {
 		let c1 = self.ack_map.merge(&other.ack_map);
 		let c2 = self.sync_map.merge(&other.sync_map);
 		let c3 = self.sync_ack_map.merge(&other.sync_ack_map);
 		c1 || c2 || c3
 	}
 }
--- a/src/rpc/layout/test.rs
+++ b/src/rpc/layout/test.rs
@ -0,0 +1,157 @@
 use std::cmp::min;
 use std::collections::HashMap;
 use garage_util::crdt::Crdt;
 use garage_util::error::*;
 use crate::layout::*;
 // This function checks that the partition size S computed is at least better than the
 // one given by a very naive algorithm. To do so, we try to run the naive algorithm
 // assuming a partion size of S+1. If we succed, it means that the optimal assignment
 // was not optimal. The naive algorithm is the following :
 // - we compute the max number of partitions associated to every node, capped at the
 // partition number. It gives the number of tokens of every node.
 // - every zone has a number of tokens equal to the sum of the tokens of its nodes.
 // - we cycle over the partitions and associate zone tokens while respecting the
 // zone redundancy constraint.
 // NOTE: the naive algorithm is not optimal. Counter example:
 // take nb_partition = 3  ; replication_factor = 5; redundancy = 4;
 // number of tokens by zone : (A, 4), (B,1), (C,4), (D, 4), (E, 2)
 // With these parameters, the naive algo fails, whereas there is a solution:
 // (A,A,C,D,E) , (A,B,C,D,D) (A,C,C,D,E)
 fn check_against_naive(cl: &LayoutVersion) -> Result<bool, Error> {
 	let over_size = cl.partition_size + 1;
 	let mut zone_token = HashMap::<String, usize>::new();
 	let (zones, zone_to_id) = cl.generate_nongateway_zone_ids()?;
 	if zones.is_empty() {
 		return Ok(false);
 	}
 	for z in zones.iter() {
 		zone_token.insert(z.clone(), 0);
 	}
 	for uuid in cl.nongateway_nodes() {
 		let z = cl.get_node_zone(&uuid)?;
 		let c = cl.get_node_capacity(&uuid).unwrap();
 		zone_token.insert(
 			z.to_string(),
 			zone_token[z] + min(NB_PARTITIONS, (c / over_size) as usize),
 		);
 	}
 	// For every partition, we count the number of zone already associated and
 	// the name of the last zone associated
 	let mut id_zone_token = vec![0; zones.len()];
 	for (z, t) in zone_token.iter() {
 		id_zone_token[zone_to_id[z]] = *t;
 	}
 	let mut nb_token = vec![0; NB_PARTITIONS];
 	let mut last_zone = vec![zones.len(); NB_PARTITIONS];
 	let mut curr_zone = 0;
 	let redundancy = cl.effective_zone_redundancy();
 	for replic in 0..cl.replication_factor {
 		for p in 0..NB_PARTITIONS {
 			while id_zone_token[curr_zone] == 0
 				|| (last_zone[p] == curr_zone
 					&& redundancy - nb_token[p] <= cl.replication_factor - replic)
 			{
 				curr_zone += 1;
 				if curr_zone >= zones.len() {
 					return Ok(true);
 				}
 			}
 			id_zone_token[curr_zone] -= 1;
 			if last_zone[p] != curr_zone {
 				nb_token[p] += 1;
 				last_zone[p] = curr_zone;
 			}
 		}
 	}
 	return Ok(false);
 }
 fn show_msg(msg: &Message) {
 	for s in msg.iter() {
 		println!("{}", s);
 	}
 }
 fn update_layout(
 	cl: &mut LayoutHistory,
 	node_capacity_vec: &[u64],
 	node_zone_vec: &[&'static str],
 	zone_redundancy: usize,
 ) {
 	let staging = cl.staging.get_mut();
 	for (i, (capacity, zone)) in node_capacity_vec
 		.iter()
 		.zip(node_zone_vec.iter())
 		.enumerate()
 	{
 		let node_id = [i as u8; 32].into();
 		let update = staging.roles.update_mutator(
 			node_id,
 			NodeRoleV(Some(NodeRole {
 				zone: zone.to_string(),
 				capacity: Some(*capacity),
 				tags: (vec![]),
 			})),
 		);
 		staging.roles.merge(&update);
 	}
 	staging.parameters.update(LayoutParameters {
 		zone_redundancy: ZoneRedundancy::AtLeast(zone_redundancy),
 	});
 }
 #[test]
 fn test_assignment() {
 	let mut node_capacity_vec = vec![4000, 1000, 2000];
 	let mut node_zone_vec = vec!["A", "B", "C"];
 	let mut cl = LayoutHistory::new(3);
 	update_layout(&mut cl, &node_capacity_vec, &node_zone_vec, 3);
 	let v = cl.current().version;
 	let (mut cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 	show_msg(&msg);
 	assert_eq!(cl.check(), Ok(()));
 	assert!(check_against_naive(cl.current()).unwrap());
 	node_capacity_vec = vec![4000, 1000, 1000, 3000, 1000, 1000, 2000, 10000, 2000];
 	node_zone_vec = vec!["A", "B", "C", "C", "C", "B", "G", "H", "I"];
 	update_layout(&mut cl, &node_capacity_vec, &node_zone_vec, 2);
 	let v = cl.current().version;
 	let (mut cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 	show_msg(&msg);
 	assert_eq!(cl.check(), Ok(()));
 	assert!(check_against_naive(cl.current()).unwrap());
 	node_capacity_vec = vec![4000, 1000, 2000, 7000, 1000, 1000, 2000, 10000, 2000];
 	update_layout(&mut cl, &node_capacity_vec, &node_zone_vec, 3);
 	let v = cl.current().version;
 	let (mut cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 	show_msg(&msg);
 	assert_eq!(cl.check(), Ok(()));
 	assert!(check_against_naive(cl.current()).unwrap());
 	node_capacity_vec = vec![
 		4000000, 4000000, 2000000, 7000000, 1000000, 9000000, 2000000, 10000, 2000000,
 	];
 	update_layout(&mut cl, &node_capacity_vec, &node_zone_vec, 1);
 	let v = cl.current().version;
 	let (cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 	show_msg(&msg);
 	assert_eq!(cl.check(), Ok(()));
 	assert!(check_against_naive(cl.current()).unwrap());
 }
--- a/src/rpc/layout/version.rs
+++ b/src/rpc/layout/version.rs
@ -1,375 +1,56 @@
 use std::cmp::Ordering;
 use std::collections::HashMap;
 use std::collections::HashSet;
-use std::fmt;
+use std::convert::TryInto;
 use bytesize::ByteSize;
 use itertools::Itertools;
-use garage_util::crdt::{AutoCrdt, Crdt, Lww, LwwMap};
+use garage_util::crdt::{Crdt, LwwMap};
 use garage_util::data::*;
 use garage_util::encode::nonversioned_encode;
 use garage_util::error::*;
-use crate::graph_algo::*;
+use super::graph_algo::*;
-
+use super::schema::*;
-use crate::ring::*;
+use super::*;
 use std::convert::TryInto;
 const NB_PARTITIONS: usize = 1usize << PARTITION_BITS;
 // The Message type will be used to collect information on the algorithm.
-type Message = Vec<String>;
+pub type Message = Vec<String>;
-mod v08 {
+impl LayoutVersion {
 	use crate::ring::CompactNodeType;
 	use garage_util::crdt::LwwMap;
 	use garage_util::data::{Hash, Uuid};
 	use serde::{Deserialize, Serialize};
 	/// The layout of the cluster, i.e. the list of roles
 	/// which are assigned to each cluster node
 	#[derive(Clone, Debug, Serialize, Deserialize)]
 	pub struct ClusterLayout {
 		pub version: u64,
 		pub replication_factor: usize,
 		pub roles: LwwMap<Uuid, NodeRoleV>,
 		/// node_id_vec: a vector of node IDs with a role assigned
 		/// in the system (this includes gateway nodes).
 		/// The order here is different than the vec stored by `roles`, because:
 		/// 1. non-gateway nodes are first so that they have lower numbers
 		/// 2. nodes that don't have a role are excluded (but they need to
 		///    stay in the CRDT as tombstones)
 		pub node_id_vec: Vec<Uuid>,
 		/// the assignation of data partitions to node, the values
 		/// are indices in node_id_vec
 		#[serde(with = "serde_bytes")]
 		pub ring_assignation_data: Vec<CompactNodeType>,
 		/// Role changes which are staged for the next version of the layout
 		pub staging: LwwMap<Uuid, NodeRoleV>,
 		pub staging_hash: Hash,
 	}
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
 	pub struct NodeRoleV(pub Option<NodeRole>);
 	/// The user-assigned roles of cluster nodes
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Debug, Serialize, Deserialize)]
 	pub struct NodeRole {
 		/// Datacenter at which this entry belong. This information is used to
 		/// perform a better geodistribution
 		pub zone: String,
 		/// The capacity of the node
 		/// If this is set to None, the node does not participate in storing data for the system
 		/// and is only active as an API gateway to other nodes
 		pub capacity: Option<u64>,
 		/// A set of tags to recognize the node
 		pub tags: Vec<String>,
 	}
 	impl garage_util::migrate::InitialFormat for ClusterLayout {}
 }
 mod v09 {
 	use super::v08;
 	use crate::ring::CompactNodeType;
 	use garage_util::crdt::{Lww, LwwMap};
 	use garage_util::data::{Hash, Uuid};
 	use serde::{Deserialize, Serialize};
 	pub use v08::{NodeRole, NodeRoleV};
 	/// The layout of the cluster, i.e. the list of roles
 	/// which are assigned to each cluster node
 	#[derive(Clone, Debug, Serialize, Deserialize)]
 	pub struct ClusterLayout {
 		pub version: u64,
 		pub replication_factor: usize,
 		/// This attribute is only used to retain the previously computed partition size,
 		/// to know to what extent does it change with the layout update.
 		pub partition_size: u64,
 		/// Parameters used to compute the assignment currently given by
 		/// ring_assignment_data
 		pub parameters: LayoutParameters,
 		pub roles: LwwMap<Uuid, NodeRoleV>,
 		/// see comment in v08::ClusterLayout
 		pub node_id_vec: Vec<Uuid>,
 		/// see comment in v08::ClusterLayout
 		#[serde(with = "serde_bytes")]
 		pub ring_assignment_data: Vec<CompactNodeType>,
 		/// Parameters to be used in the next partition assignment computation.
 		pub staging_parameters: Lww<LayoutParameters>,
 		/// Role changes which are staged for the next version of the layout
 		pub staging_roles: LwwMap<Uuid, NodeRoleV>,
 		pub staging_hash: Hash,
 	}
 	/// This struct is used to set the parameters to be used in the assignment computation
 	/// algorithm. It is stored as a Crdt.
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug, Serialize, Deserialize)]
 	pub struct LayoutParameters {
 		pub zone_redundancy: ZoneRedundancy,
 	}
 	/// Zone redundancy: if set to AtLeast(x), the layout calculation will aim to store copies
 	/// of each partition on at least that number of different zones.
 	/// Otherwise, copies will be stored on the maximum possible number of zones.
 	#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug, Serialize, Deserialize)]
 	pub enum ZoneRedundancy {
 		AtLeast(usize),
 		Maximum,
 	}
 	impl garage_util::migrate::Migrate for ClusterLayout {
 		const VERSION_MARKER: &'static [u8] = b"G09layout";
 		type Previous = v08::ClusterLayout;
 		fn migrate(previous: Self::Previous) -> Self {
 			use itertools::Itertools;
 			// In the old layout, capacities are in an arbitrary unit,
 			// but in the new layout they are in bytes.
 			// Here we arbitrarily multiply everything by 1G,
 			// such that 1 old capacity unit = 1GB in the new units.
 			// This is totally arbitrary and won't work for most users.
 			let cap_mul = 1024 * 1024 * 1024;
 			let roles = multiply_all_capacities(previous.roles, cap_mul);
 			let staging_roles = multiply_all_capacities(previous.staging, cap_mul);
 			let node_id_vec = previous.node_id_vec;
 			// Determine partition size
 			let mut tmp = previous.ring_assignation_data.clone();
 			tmp.sort();
 			let partition_size = tmp
 				.into_iter()
 				.dedup_with_count()
 				.map(|(npart, node)| {
 					roles
 						.get(&node_id_vec[node as usize])
 						.and_then(|p| p.0.as_ref().and_then(|r| r.capacity))
 						.unwrap_or(0) / npart as u64
 				})
 				.min()
 				.unwrap_or(0);
 			// By default, zone_redundancy is maximum possible value
 			let parameters = LayoutParameters {
 				zone_redundancy: ZoneRedundancy::Maximum,
 			};
 			let mut res = Self {
 				version: previous.version,
 				replication_factor: previous.replication_factor,
 				partition_size,
 				parameters,
 				roles,
 				node_id_vec,
 				ring_assignment_data: previous.ring_assignation_data,
 				staging_parameters: Lww::new(parameters),
 				staging_roles,
 				staging_hash: [0u8; 32].into(),
 			};
 			res.staging_hash = res.calculate_staging_hash();
 			res
 		}
 	}
 	fn multiply_all_capacities(
 		old_roles: LwwMap<Uuid, NodeRoleV>,
 		mul: u64,
 	) -> LwwMap<Uuid, NodeRoleV> {
 		let mut new_roles = LwwMap::new();
 		for (node, ts, role) in old_roles.items() {
 			let mut role = role.clone();
 			if let NodeRoleV(Some(NodeRole {
 				capacity: Some(ref mut cap),
 				..
 			})) = role
 			{
 				*cap *= mul;
 			}
 			new_roles.merge_raw(node, *ts, &role);
 		}
 		new_roles
 	}
 }
 pub use v09::*;
 impl AutoCrdt for LayoutParameters {
 	const WARN_IF_DIFFERENT: bool = true;
 }
 impl AutoCrdt for NodeRoleV {
 	const WARN_IF_DIFFERENT: bool = true;
 }
 impl NodeRole {
 	pub fn capacity_string(&self) -> String {
 		match self.capacity {
 			Some(c) => ByteSize::b(c).to_string_as(false),
 			None => "gateway".to_string(),
 		}
 	}
 	pub fn tags_string(&self) -> String {
 		self.tags.join(",")
 	}
 }
 impl fmt::Display for ZoneRedundancy {
 	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 		match self {
 			ZoneRedundancy::Maximum => write!(f, "maximum"),
 			ZoneRedundancy::AtLeast(x) => write!(f, "{}", x),
 		}
 	}
 }
 impl core::str::FromStr for ZoneRedundancy {
 	type Err = &'static str;
 	fn from_str(s: &str) -> Result<Self, Self::Err> {
 		match s {
 			"none" | "max" | "maximum" => Ok(ZoneRedundancy::Maximum),
 			x => {
 				let v = x
 					.parse::<usize>()
 					.map_err(|_| "zone redundancy must be 'none'/'max' or an integer")?;
 				Ok(ZoneRedundancy::AtLeast(v))
 			}
 		}
 	}
 }
 // Implementation of the ClusterLayout methods unrelated to the assignment algorithm.
 impl ClusterLayout {
 	pub fn new(replication_factor: usize) -> Self {
 		// We set the default zone redundancy to be Maximum, meaning that the maximum
 		// possible value will be used depending on the cluster topology
 		let parameters = LayoutParameters {
 			zone_redundancy: ZoneRedundancy::Maximum,
 		};
 		let staging_parameters = Lww::<LayoutParameters>::new(parameters);
-		let empty_lwwmap = LwwMap::new();
+		LayoutVersion {
 		let mut ret = ClusterLayout {
 			version: 0,
 			replication_factor,
 			partition_size: 0,
 			roles: LwwMap::new(),
 			node_id_vec: Vec::new(),
 			nongateway_node_count: 0,
 			ring_assignment_data: Vec::new(),
 			parameters,
 			staging_parameters,
 			staging_roles: empty_lwwmap,
 			staging_hash: [0u8; 32].into(),
 		};
 		ret.staging_hash = ret.calculate_staging_hash();
 		ret
 	}
 	fn calculate_staging_hash(&self) -> Hash {
 		let hashed_tuple = (&self.staging_roles, &self.staging_parameters);
 		blake2sum(&nonversioned_encode(&hashed_tuple).unwrap()[..])
 	}
 	pub fn merge(&mut self, other: &ClusterLayout) -> bool {
 		match other.version.cmp(&self.version) {
 			Ordering::Greater => {
 				*self = other.clone();
 				true
 			}
 			Ordering::Equal => {
 				self.staging_parameters.merge(&other.staging_parameters);
 				self.staging_roles.merge(&other.staging_roles);
 				let new_staging_hash = self.calculate_staging_hash();
 				let changed = new_staging_hash != self.staging_hash;
 				self.staging_hash = new_staging_hash;
 				changed
 			}
 			Ordering::Less => false,
 		}
 	}
-	pub fn apply_staged_changes(mut self, version: Option<u64>) -> Result<(Self, Message), Error> {
+	// ===================== accessors ======================
 		match version {
 			None => {
 				let error = r#"
 Please pass the new layout version number to ensure that you are writing the correct version of the cluster layout.
 To know the correct value of the new layout version, invoke `garage layout show` and review the proposed changes.
 				"#;
 				return Err(Error::Message(error.into()));
 			}
 			Some(v) => {
 				if v != self.version + 1 {
 					return Err(Error::Message("Invalid new layout version".into()));
 				}
 			}
 		}
-		self.roles.merge(&self.staging_roles);
+	/// Returns a list of IDs of nodes that have a role in this
-		self.roles.retain(|(_, _, v)| v.0.is_some());
+	/// version of the cluster layout, including gateway nodes
-		self.parameters = *self.staging_parameters.get();
+	pub fn all_nodes(&self) -> &[Uuid] {
 		self.staging_roles.clear();
 		self.staging_hash = self.calculate_staging_hash();
 		let msg = self.calculate_partition_assignment()?;
 		self.version += 1;
 		Ok((self, msg))
 	}
 	pub fn revert_staged_changes(mut self, version: Option<u64>) -> Result<Self, Error> {
 		match version {
 			None => {
 				let error = r#"
 Please pass the new layout version number to ensure that you are writing the correct version of the cluster layout.
 To know the correct value of the new layout version, invoke `garage layout show` and review the proposed changes.
 				"#;
 				return Err(Error::Message(error.into()));
 			}
 			Some(v) => {
 				if v != self.version + 1 {
 					return Err(Error::Message("Invalid new layout version".into()));
 				}
 			}
 		}
 		self.staging_roles.clear();
 		self.staging_parameters.update(self.parameters);
 		self.staging_hash = self.calculate_staging_hash();
 		self.version += 1;
 		Ok(self)
 	}
 	/// Returns a list of IDs of nodes that currently have
 	/// a role in the cluster
 	pub fn node_ids(&self) -> &[Uuid] {
 		&self.node_id_vec[..]
 	}
-	pub fn num_nodes(&self) -> usize {
+	/// Returns a list of IDs of nodes that have a storage capacity
-		self.node_id_vec.len()
+	/// assigned in this version of the cluster layout
 	pub fn nongateway_nodes(&self) -> &[Uuid] {
 		&self.node_id_vec[..self.nongateway_node_count]
 	}
-	/// Returns the role of a node in the layout
+	/// Returns the role of a node in the layout, if it has one
 	pub fn node_role(&self, node: &Uuid) -> Option<&NodeRole> {
 		match self.roles.get(node) {
 			Some(NodeRoleV(Some(v))) => Some(v),
@ -377,41 +58,15 @@ To know the correct value of the new layout version, invoke `garage layout show`
 		}
 	}
-	/// Returns the uuids of the non_gateway nodes in self.node_id_vec.
+	/// Returns the capacity of a node in the layout, if it has one
-	fn nongateway_nodes(&self) -> Vec<Uuid> {
+	pub fn get_node_capacity(&self, uuid: &Uuid) -> Option<u64> {
 		let mut result = Vec::<Uuid>::new();
 		for uuid in self.node_id_vec.iter() {
 			match self.node_role(uuid) {
 				Some(role) if role.capacity.is_some() => result.push(*uuid),
 				_ => (),
 			}
 		}
 		result
 	}
 	/// Given a node uuids, this function returns the label of its zone
 	fn get_node_zone(&self, uuid: &Uuid) -> Result<String, Error> {
 		match self.node_role(uuid) {
 			Some(role) => Ok(role.zone.clone()),
 			_ => Err(Error::Message(
 				"The Uuid does not correspond to a node present in the cluster.".into(),
 			)),
 		}
 	}
 	/// Given a node uuids, this function returns its capacity or fails if it does not have any
 	pub fn get_node_capacity(&self, uuid: &Uuid) -> Result<u64, Error> {
 		match self.node_role(uuid) {
 			Some(NodeRole {
 				capacity: Some(cap),
 				zone: _,
 				tags: _,
-			}) => Ok(*cap),
+			}) => Some(*cap),
-			_ => Err(Error::Message(
+			_ => None,
 				"The Uuid does not correspond to a node present in the \
                    cluster or this node does not have a positive capacity."
 					.into(),
 			)),
 		}
 	}
@ -435,17 +90,71 @@ To know the correct value of the new layout version, invoke `garage layout show`
 		))
 	}
 	/// Get the partition in which data would fall on
 	pub fn partition_of(&self, position: &Hash) -> Partition {
 		let top = u16::from_be_bytes(position.as_slice()[0..2].try_into().unwrap());
 		top >> (16 - PARTITION_BITS)
 	}
 	/// Get the list of partitions and the first hash of a partition key that would fall in it
 	pub fn partitions(&self) -> impl Iterator<Item = (Partition, Hash)> + '_ {
 		(0..(1 << PARTITION_BITS)).map(|i| {
 			let top = (i as u16) << (16 - PARTITION_BITS);
 			let mut location = [0u8; 32];
 			location[..2].copy_from_slice(&u16::to_be_bytes(top)[..]);
 			(i as u16, Hash::from(location))
 		})
 	}
 	/// Return the n servers in which data for this hash should be replicated
 	pub fn nodes_of(&self, position: &Hash, n: usize) -> impl Iterator<Item = Uuid> + '_ {
 		assert_eq!(n, self.replication_factor);
 		let data = &self.ring_assignment_data;
 		let partition_nodes = if data.len() == self.replication_factor * (1 << PARTITION_BITS) {
 			let partition_idx = self.partition_of(position) as usize;
 			let partition_start = partition_idx * self.replication_factor;
 			let partition_end = (partition_idx + 1) * self.replication_factor;
 			&data[partition_start..partition_end]
 		} else {
 			warn!("Ring not yet ready, read/writes will be lost!");
 			&[]
 		};
 		partition_nodes
 			.iter()
 			.map(move |i| self.node_id_vec[*i as usize])
 	}
 	// ===================== internal information extractors ======================
 	/// Given a node uuids, this function returns the label of its zone
 	pub(crate) fn get_node_zone(&self, uuid: &Uuid) -> Result<&str, Error> {
 		match self.node_role(uuid) {
 			Some(role) => Ok(&role.zone),
 			_ => Err(Error::Message(
 				"The Uuid does not correspond to a node present in the cluster.".into(),
 			)),
 		}
 	}
 	fn expect_get_node_capacity(&self, uuid: &Uuid) -> u64 {
 		self.get_node_capacity(&uuid)
 			.expect("non-gateway node with zero capacity")
 	}
 	/// Returns the sum of capacities of non gateway nodes in the cluster
 	fn get_total_capacity(&self) -> Result<u64, Error> {
 		let mut total_capacity = 0;
-		for uuid in self.nongateway_nodes().iter() {
+		for uuid in self.nongateway_nodes() {
-			total_capacity += self.get_node_capacity(uuid)?;
+			total_capacity += self.expect_get_node_capacity(&uuid);
 		}
 		Ok(total_capacity)
 	}
 	/// Returns the effective value of the zone_redundancy parameter
-	fn effective_zone_redundancy(&self) -> usize {
+	pub(crate) fn effective_zone_redundancy(&self) -> usize {
 		match self.parameters.zone_redundancy {
 			ZoneRedundancy::AtLeast(v) => v,
 			ZoneRedundancy::Maximum => {
@ -465,10 +174,14 @@ To know the correct value of the new layout version, invoke `garage layout show`
 	/// (assignment, roles, parameters, partition size)
 	/// returns true if consistent, false if error
 	pub fn check(&self) -> Result<(), String> {
-		// Check that the hash of the staging data is correct
+		// Check that the assignment data has the correct length
-		let staging_hash = self.calculate_staging_hash();
+		let expected_assignment_data_len = (1 << PARTITION_BITS) * self.replication_factor;
-		if staging_hash != self.staging_hash {
+		if self.ring_assignment_data.len() != expected_assignment_data_len {
-			return Err("staging_hash is incorrect".into());
+			return Err(format!(
 				"ring_assignment_data has incorrect length {} instead of {}",
 				self.ring_assignment_data.len(),
 				expected_assignment_data_len
 			));
 		}
 		// Check that node_id_vec contains the correct list of nodes
@ -486,16 +199,6 @@ To know the correct value of the new layout version, invoke `garage layout show`
 			return Err(format!("node_id_vec does not contain the correct set of nodes\nnode_id_vec: {:?}\nexpected: {:?}", node_id_vec, expected_nodes));
 		}
 		// Check that the assignment data has the correct length
 		let expected_assignment_data_len = (1 << PARTITION_BITS) * self.replication_factor;
 		if self.ring_assignment_data.len() != expected_assignment_data_len {
 			return Err(format!(
 				"ring_assignment_data has incorrect length {} instead of {}",
 				self.ring_assignment_data.len(),
 				expected_assignment_data_len
 			));
 		}
 		// Check that the assigned nodes are correct identifiers
 		// of nodes that are assigned a role
 		// and that role is not the role of a gateway nodes
@ -546,7 +249,7 @@ To know the correct value of the new layout version, invoke `garage layout show`
 			if *usage > 0 {
 				let uuid = self.node_id_vec[n];
 				let partusage = usage * self.partition_size;
-				let nodecap = self.get_node_capacity(&uuid).unwrap();
+				let nodecap = self.expect_get_node_capacity(&uuid);
 				if partusage > nodecap {
 					return Err(format!(
 						"node usage ({}) is bigger than node capacity ({})",
@ -574,12 +277,24 @@ To know the correct value of the new layout version, invoke `garage layout show`
 		Ok(())
 	}
 }
-// ====================================================================================
+	// ================== updates to layout, internals ===================
 	pub(crate) fn calculate_next_version(
 		mut self,
 		staging: &LayoutStaging,
 	) -> Result<(Self, Message), Error> {
 		self.version += 1;
 		self.roles.merge(&staging.roles);
 		self.roles.retain(|(_, _, v)| v.0.is_some());
 		self.parameters = *staging.parameters.get();
 		let msg = self.calculate_partition_assignment()?;
 		Ok((self, msg))
 	}
 // Implementation of the ClusterLayout methods related to the assignment algorithm.
 impl ClusterLayout {
 	/// This function calculates a new partition-to-node assignment.
 	/// The computed assignment respects the node replication factor
 	/// and the zone redundancy parameter It maximizes the capacity of a
@ -609,12 +324,12 @@ impl ClusterLayout {
 		// to use them as indices in the flow graphs.
 		let (id_to_zone, zone_to_id) = self.generate_nongateway_zone_ids()?;
-		let nb_nongateway_nodes = self.nongateway_nodes().len();
+		if self.nongateway_nodes().len() < self.replication_factor {
 		if nb_nongateway_nodes < self.replication_factor {
 			return Err(Error::Message(format!(
 				"The number of nodes with positive \
            capacity ({}) is smaller than the replication factor ({}).",
-				nb_nongateway_nodes, self.replication_factor
+				self.nongateway_nodes().len(),
 				self.replication_factor
 			)));
 		}
 		if id_to_zone.len() < zone_redundancy {
@ -712,12 +427,14 @@ impl ClusterLayout {
 			.map(|(k, _, _)| *k)
 			.collect();
-		let mut new_node_id_vec = Vec::<Uuid>::new();
+		let old_node_id_vec = std::mem::take(&mut self.node_id_vec);
 		new_node_id_vec.extend(new_non_gateway_nodes);
 		new_node_id_vec.extend(new_gateway_nodes);
-		let old_node_id_vec = self.node_id_vec.clone();
+		self.nongateway_node_count = new_non_gateway_nodes.len();
-		self.node_id_vec = new_node_id_vec.clone();
+		self.node_id_vec.clear();
 		self.node_id_vec.extend(new_non_gateway_nodes);
 		self.node_id_vec.extend(new_gateway_nodes);
 		let new_node_id_vec = &self.node_id_vec;
 		// (2) We retrieve the old association
 		// We rewrite the old association with the new indices. We only consider partition
@ -756,7 +473,7 @@ impl ClusterLayout {
 			}
 		}
-		// We write the ring
+		// We clear the ring assignemnt data
 		self.ring_assignment_data = Vec::<CompactNodeType>::new();
 		Ok(Some(old_assignment))
@ -764,7 +481,9 @@ impl ClusterLayout {
 	/// This function generates ids for the zone of the nodes appearing in
 	/// self.node_id_vec.
-	fn generate_nongateway_zone_ids(&self) -> Result<(Vec<String>, HashMap<String, usize>), Error> {
+	pub(crate) fn generate_nongateway_zone_ids(
 		&self,
 	) -> Result<(Vec<String>, HashMap<String, usize>), Error> {
 		let mut id_to_zone = Vec::<String>::new();
 		let mut zone_to_id = HashMap::<String, usize>::new();
@ -846,7 +565,7 @@ impl ClusterLayout {
 		zone_redundancy: usize,
 	) -> Result<Graph<FlowEdge>, Error> {
 		let vertices =
-			ClusterLayout::generate_graph_vertices(zone_to_id.len(), self.nongateway_nodes().len());
+			LayoutVersion::generate_graph_vertices(zone_to_id.len(), self.nongateway_nodes().len());
 		let mut g = Graph::<FlowEdge>::new(&vertices);
 		let nb_zones = zone_to_id.len();
 		for p in 0..NB_PARTITIONS {
@ -866,8 +585,8 @@ impl ClusterLayout {
 			}
 		}
 		for n in 0..self.nongateway_nodes().len() {
-			let node_capacity = self.get_node_capacity(&self.node_id_vec[n])?;
+			let node_capacity = self.expect_get_node_capacity(&self.node_id_vec[n]);
-			let node_zone = zone_to_id[&self.get_node_zone(&self.node_id_vec[n])?];
+			let node_zone = zone_to_id[self.get_node_zone(&self.node_id_vec[n])?];
 			g.add_edge(Vertex::N(n), Vertex::Sink, node_capacity / partition_size)?;
 			for p in 0..NB_PARTITIONS {
 				if !exclude_assoc.contains(&(p, n)) {
@ -913,7 +632,7 @@ impl ClusterLayout {
 		// The algorithm is such that it will start with the flow that we just computed
 		// and find ameliorating paths from that.
 		for (p, n) in exclude_edge.iter() {
-			let node_zone = zone_to_id[&self.get_node_zone(&self.node_id_vec[*n])?];
+			let node_zone = zone_to_id[self.get_node_zone(&self.node_id_vec[*n])?];
 			g.add_edge(Vertex::PZ(*p, node_zone), Vertex::N(*n), 1)?;
 		}
 		g.compute_maximal_flow()?;
@ -933,7 +652,7 @@ impl ClusterLayout {
 		let mut cost = CostFunction::new();
 		for (p, assoc_p) in prev_assign.iter().enumerate() {
 			for n in assoc_p.iter() {
-				let node_zone = zone_to_id[&self.get_node_zone(&self.node_id_vec[*n])?];
+				let node_zone = zone_to_id[self.get_node_zone(&self.node_id_vec[*n])?];
 				cost.insert((Vertex::PZ(p, node_zone), Vertex::N(*n)), -1);
 			}
 		}
@ -1035,7 +754,7 @@ impl ClusterLayout {
 						let mut old_zones_of_p = Vec::<usize>::new();
 						for n in prev_assign[p].iter() {
 							old_zones_of_p
-								.push(zone_to_id[&self.get_node_zone(&self.node_id_vec[*n])?]);
+								.push(zone_to_id[self.get_node_zone(&self.node_id_vec[*n])?]);
 						}
 						if !old_zones_of_p.contains(&z) {
 							new_partitions_zone[z] += 1;
@ -1091,13 +810,13 @@ impl ClusterLayout {
 			let available_cap_z: u64 = self.partition_size * replicated_partitions as u64;
 			let mut total_cap_z = 0;
 			for n in nodes_of_z.iter() {
-				total_cap_z += self.get_node_capacity(&self.node_id_vec[*n])?;
+				total_cap_z += self.expect_get_node_capacity(&self.node_id_vec[*n]);
 			}
 			let percent_cap_z = 100.0 * (available_cap_z as f32) / (total_cap_z as f32);
 			for n in nodes_of_z.iter() {
 				let available_cap_n = stored_partitions[*n] as u64 * self.partition_size;
-				let total_cap_n = self.get_node_capacity(&self.node_id_vec[*n])?;
+				let total_cap_n = self.expect_get_node_capacity(&self.node_id_vec[*n]);
 				let tags_n = (self.node_role(&self.node_id_vec[*n]).ok_or("<??>"))?.tags_string();
 				table.push(format!(
 					"  {:?}\t{}\t{} ({} new)\t{}\t{} ({:.1}%)",
@ -1127,167 +846,3 @@ impl ClusterLayout {
 		Ok(msg)
 	}
 }
 // ====================================================================================
 #[cfg(test)]
 mod tests {
 	use super::{Error, *};
 	use std::cmp::min;
 	// This function checks that the partition size S computed is at least better than the
 	// one given by a very naive algorithm. To do so, we try to run the naive algorithm
 	// assuming a partion size of S+1. If we succed, it means that the optimal assignment
 	// was not optimal. The naive algorithm is the following :
 	// - we compute the max number of partitions associated to every node, capped at the
 	// partition number. It gives the number of tokens of every node.
 	// - every zone has a number of tokens equal to the sum of the tokens of its nodes.
 	// - we cycle over the partitions and associate zone tokens while respecting the
 	// zone redundancy constraint.
 	// NOTE: the naive algorithm is not optimal. Counter example:
 	// take nb_partition = 3  ; replication_factor = 5; redundancy = 4;
 	// number of tokens by zone : (A, 4), (B,1), (C,4), (D, 4), (E, 2)
 	// With these parameters, the naive algo fails, whereas there is a solution:
 	// (A,A,C,D,E) , (A,B,C,D,D) (A,C,C,D,E)
 	fn check_against_naive(cl: &ClusterLayout) -> Result<bool, Error> {
 		let over_size = cl.partition_size + 1;
 		let mut zone_token = HashMap::<String, usize>::new();
 		let (zones, zone_to_id) = cl.generate_nongateway_zone_ids()?;
 		if zones.is_empty() {
 			return Ok(false);
 		}
 		for z in zones.iter() {
 			zone_token.insert(z.clone(), 0);
 		}
 		for uuid in cl.nongateway_nodes().iter() {
 			let z = cl.get_node_zone(uuid)?;
 			let c = cl.get_node_capacity(uuid)?;
 			zone_token.insert(
 				z.clone(),
 				zone_token[&z] + min(NB_PARTITIONS, (c / over_size) as usize),
 			);
 		}
 		// For every partition, we count the number of zone already associated and
 		// the name of the last zone associated
 		let mut id_zone_token = vec![0; zones.len()];
 		for (z, t) in zone_token.iter() {
 			id_zone_token[zone_to_id[z]] = *t;
 		}
 		let mut nb_token = vec![0; NB_PARTITIONS];
 		let mut last_zone = vec![zones.len(); NB_PARTITIONS];
 		let mut curr_zone = 0;
 		let redundancy = cl.effective_zone_redundancy();
 		for replic in 0..cl.replication_factor {
 			for p in 0..NB_PARTITIONS {
 				while id_zone_token[curr_zone] == 0
 					|| (last_zone[p] == curr_zone
 						&& redundancy - nb_token[p] <= cl.replication_factor - replic)
 				{
 					curr_zone += 1;
 					if curr_zone >= zones.len() {
 						return Ok(true);
 					}
 				}
 				id_zone_token[curr_zone] -= 1;
 				if last_zone[p] != curr_zone {
 					nb_token[p] += 1;
 					last_zone[p] = curr_zone;
 				}
 			}
 		}
 		return Ok(false);
 	}
 	fn show_msg(msg: &Message) {
 		for s in msg.iter() {
 			println!("{}", s);
 		}
 	}
 	fn update_layout(
 		cl: &mut ClusterLayout,
 		node_id_vec: &Vec<u8>,
 		node_capacity_vec: &Vec<u64>,
 		node_zone_vec: &Vec<String>,
 		zone_redundancy: usize,
 	) {
 		for i in 0..node_id_vec.len() {
 			if let Some(x) = FixedBytes32::try_from(&[i as u8; 32]) {
 				cl.node_id_vec.push(x);
 			}
 			let update = cl.staging_roles.update_mutator(
 				cl.node_id_vec[i],
 				NodeRoleV(Some(NodeRole {
 					zone: (node_zone_vec[i].to_string()),
 					capacity: (Some(node_capacity_vec[i])),
 					tags: (vec![]),
 				})),
 			);
 			cl.staging_roles.merge(&update);
 		}
 		cl.staging_parameters.update(LayoutParameters {
 			zone_redundancy: ZoneRedundancy::AtLeast(zone_redundancy),
 		});
 		cl.staging_hash = cl.calculate_staging_hash();
 	}
 	#[test]
 	fn test_assignment() {
 		let mut node_id_vec = vec![1, 2, 3];
 		let mut node_capacity_vec = vec![4000, 1000, 2000];
 		let mut node_zone_vec = vec!["A", "B", "C"]
 			.into_iter()
 			.map(|x| x.to_string())
 			.collect();
 		let mut cl = ClusterLayout::new(3);
 		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec, 3);
 		let v = cl.version;
 		let (mut cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 		show_msg(&msg);
 		assert_eq!(cl.check(), Ok(()));
 		assert!(matches!(check_against_naive(&cl), Ok(true)));
 		node_id_vec = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
 		node_capacity_vec = vec![4000, 1000, 1000, 3000, 1000, 1000, 2000, 10000, 2000];
 		node_zone_vec = vec!["A", "B", "C", "C", "C", "B", "G", "H", "I"]
 			.into_iter()
 			.map(|x| x.to_string())
 			.collect();
 		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec, 2);
 		let v = cl.version;
 		let (mut cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 		show_msg(&msg);
 		assert_eq!(cl.check(), Ok(()));
 		assert!(matches!(check_against_naive(&cl), Ok(true)));
 		node_capacity_vec = vec![4000, 1000, 2000, 7000, 1000, 1000, 2000, 10000, 2000];
 		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec, 3);
 		let v = cl.version;
 		let (mut cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 		show_msg(&msg);
 		assert_eq!(cl.check(), Ok(()));
 		assert!(matches!(check_against_naive(&cl), Ok(true)));
 		node_capacity_vec = vec![
 			4000000, 4000000, 2000000, 7000000, 1000000, 9000000, 2000000, 10000, 2000000,
 		];
 		update_layout(&mut cl, &node_id_vec, &node_capacity_vec, &node_zone_vec, 1);
 		let v = cl.version;
 		let (cl, msg) = cl.apply_staged_changes(Some(v + 1)).unwrap();
 		show_msg(&msg);
 		assert_eq!(cl.check(), Ok(()));
 		assert!(matches!(check_against_naive(&cl), Ok(true)));
 	}
 }
--- a/src/rpc/lib.rs
+++ b/src/rpc/lib.rs
@ -11,10 +11,8 @@ mod consul;
 #[cfg(feature = "kubernetes-discovery")]
 mod kubernetes;
 pub mod graph_algo;
 pub mod layout;
 pub mod replication_mode;
 pub mod ring;
 pub mod system;
 pub mod rpc_helper;
--- a/src/rpc/ring.rs
+++ b/src/rpc/ring.rs
@ -1,164 +0,0 @@
 //! Module containing types related to computing nodes which should receive a copy of data blocks
 //! and metadata
 use std::convert::TryInto;
 use garage_util::data::*;
 use crate::layout::ClusterLayout;
 /// A partition id, which is stored on 16 bits
 /// i.e. we have up to 2**16 partitions.
 /// (in practice we have exactly 2**PARTITION_BITS partitions)
 pub type Partition = u16;
 // TODO: make this constant parametrizable in the config file
 // For deployments with many nodes it might make sense to bump
 // it up to 10.
 // Maximum value : 16
 /// How many bits from the hash are used to make partitions. Higher numbers means more fairness in
 /// presence of numerous nodes, but exponentially bigger ring. Max 16
 pub const PARTITION_BITS: usize = 8;
 const PARTITION_MASK_U16: u16 = ((1 << PARTITION_BITS) - 1) << (16 - PARTITION_BITS);
 /// A ring distributing fairly objects to nodes
 #[derive(Clone)]
 pub struct Ring {
 	/// The replication factor for this ring
 	pub replication_factor: usize,
 	/// The network configuration used to generate this ring
 	pub layout: ClusterLayout,
 	// Internal order of nodes used to make a more compact representation of the ring
 	nodes: Vec<Uuid>,
 	// The list of entries in the ring
 	ring: Vec<RingEntry>,
 }
 // Type to store compactly the id of a node in the system
 // Change this to u16 the day we want to have more than 256 nodes in a cluster
 pub type CompactNodeType = u8;
 pub const MAX_NODE_NUMBER: usize = 256;
 // The maximum number of times an object might get replicated
 // This must be at least 3 because Garage supports 3-way replication
 // Here we use 6 so that the size of a ring entry is 8 bytes
 // (2 bytes partition id, 6 bytes node numbers as u8s)
 const MAX_REPLICATION: usize = 6;
 /// An entry in the ring
 #[derive(Clone, Debug)]
 struct RingEntry {
 	// The two first bytes of the first hash that goes in this partition
 	// (the next bytes are zeroes)
 	hash_prefix: u16,
 	// The nodes that store this partition, stored as a list of positions in the `nodes`
 	// field of the Ring structure
 	// Only items 0 up to ring.replication_factor - 1 are used, others are zeros
 	nodes_buf: [CompactNodeType; MAX_REPLICATION],
 }
 impl Ring {
 	pub(crate) fn new(layout: ClusterLayout, replication_factor: usize) -> Self {
 		if replication_factor != layout.replication_factor {
 			warn!("Could not build ring: replication factor does not match between local configuration and network role assignment.");
 			return Self::empty(layout, replication_factor);
 		}
 		if layout.ring_assignment_data.len() != replication_factor * (1 << PARTITION_BITS) {
 			warn!("Could not build ring: network role assignment data has invalid length");
 			return Self::empty(layout, replication_factor);
 		}
 		let nodes = layout.node_id_vec.clone();
 		let ring = (0..(1 << PARTITION_BITS))
 			.map(|i| {
 				let top = (i as u16) << (16 - PARTITION_BITS);
 				let mut nodes_buf = [0u8; MAX_REPLICATION];
 				nodes_buf[..replication_factor].copy_from_slice(
 					&layout.ring_assignment_data
 						[replication_factor * i..replication_factor * (i + 1)],
 				);
 				RingEntry {
 					hash_prefix: top,
 					nodes_buf,
 				}
 			})
 			.collect::<Vec<_>>();
 		Self {
 			replication_factor,
 			layout,
 			nodes,
 			ring,
 		}
 	}
 	fn empty(layout: ClusterLayout, replication_factor: usize) -> Self {
 		Self {
 			replication_factor,
 			layout,
 			nodes: vec![],
 			ring: vec![],
 		}
 	}
 	/// Get the partition in which data would fall on
 	pub fn partition_of(&self, position: &Hash) -> Partition {
 		let top = u16::from_be_bytes(position.as_slice()[0..2].try_into().unwrap());
 		top >> (16 - PARTITION_BITS)
 	}
 	/// Get the list of partitions and the first hash of a partition key that would fall in it
 	pub fn partitions(&self) -> Vec<(Partition, Hash)> {
 		let mut ret = vec![];
 		for (i, entry) in self.ring.iter().enumerate() {
 			let mut location = [0u8; 32];
 			location[..2].copy_from_slice(&u16::to_be_bytes(entry.hash_prefix)[..]);
 			ret.push((i as u16, location.into()));
 		}
 		if !ret.is_empty() {
 			assert_eq!(ret[0].1, [0u8; 32].into());
 		}
 		ret
 	}
 	/// Walk the ring to find the n servers in which data should be replicated
 	pub fn get_nodes(&self, position: &Hash, n: usize) -> Vec<Uuid> {
 		if self.ring.len() != 1 << PARTITION_BITS {
 			warn!("Ring not yet ready, read/writes will be lost!");
 			return vec![];
 		}
 		let partition_idx = self.partition_of(position) as usize;
 		let partition = &self.ring[partition_idx];
 		let top = u16::from_be_bytes(position.as_slice()[0..2].try_into().unwrap());
 		// Check that we haven't messed up our partition table, i.e. that this partition
 		// table entrey indeed corresponds to the item we are storing
 		assert_eq!(
 			partition.hash_prefix & PARTITION_MASK_U16,
 			top & PARTITION_MASK_U16
 		);
 		assert!(n <= self.replication_factor);
 		partition.nodes_buf[..n]
 			.iter()
 			.map(|i| self.nodes[*i as usize])
 			.collect::<Vec<_>>()
 	}
 }
 #[cfg(test)]
 mod tests {
 	use super::*;
 	#[test]
 	fn test_ring_entry_size() {
 		assert_eq!(std::mem::size_of::<RingEntry>(), 8);
 	}
 }
--- a/src/rpc/rpc_helper.rs
+++ b/src/rpc/rpc_helper.rs
@ -1,12 +1,12 @@
 //! Contain structs related to making RPCs
-use std::sync::Arc;
+use std::collections::HashMap;
 use std::sync::{Arc, RwLock};
 use std::time::Duration;
 use futures::future::join_all;
 use futures::stream::futures_unordered::FuturesUnordered;
 use futures::stream::StreamExt;
 use tokio::select;
 use tokio::sync::watch;
 use opentelemetry::KeyValue;
 use opentelemetry::{
@ -26,8 +26,8 @@ use garage_util::data::*;
 use garage_util::error::Error;
 use garage_util::metrics::RecordDuration;
 use crate::layout::LayoutHelper;
 use crate::metrics::RpcMetrics;
 use crate::ring::Ring;
 // Default RPC timeout = 5 minutes
 const DEFAULT_TIMEOUT: Duration = Duration::from_secs(300);
@ -36,11 +36,11 @@ const DEFAULT_TIMEOUT: Duration = Duration::from_secs(300);
 #[derive(Copy, Clone)]
 pub struct RequestStrategy {
 	/// Min number of response to consider the request successful
-	pub rs_quorum: Option<usize>,
+	rs_quorum: Option<usize>,
-	/// Should requests be dropped after enough response are received
+	/// Send all requests at once
-	pub rs_interrupt_after_quorum: bool,
+	rs_send_all_at_once: Option<bool>,
 	/// Request priority
-	pub rs_priority: RequestPriority,
+	rs_priority: RequestPriority,
 	/// Custom timeout for this request
 	rs_timeout: Timeout,
 }
@ -57,7 +57,7 @@ impl RequestStrategy {
 	pub fn with_priority(prio: RequestPriority) -> Self {
 		RequestStrategy {
 			rs_quorum: None,
-			rs_interrupt_after_quorum: false,
+			rs_send_all_at_once: None,
 			rs_priority: prio,
 			rs_timeout: Timeout::Default,
 		}
@ -67,10 +67,9 @@ impl RequestStrategy {
 		self.rs_quorum = Some(quorum);
 		self
 	}
-	/// Set if requests can be dropped after quorum has been reached
+	/// Set quorum to be reached for request
-	/// In general true for read requests, and false for write
+	pub fn send_all_at_once(mut self, value: bool) -> Self {
-	pub fn interrupt_after_quorum(mut self, interrupt: bool) -> Self {
+		self.rs_send_all_at_once = Some(value);
 		self.rs_interrupt_after_quorum = interrupt;
 		self
 	}
 	/// Deactivate timeout for this request
@ -91,7 +90,7 @@ pub struct RpcHelper(Arc<RpcHelperInner>);
 struct RpcHelperInner {
 	our_node_id: Uuid,
 	fullmesh: Arc<FullMeshPeeringStrategy>,
-	ring: watch::Receiver<Arc<Ring>>,
+	layout: Arc<RwLock<LayoutHelper>>,
 	metrics: RpcMetrics,
 	rpc_timeout: Duration,
 }
@ -100,7 +99,7 @@ impl RpcHelper {
 	pub(crate) fn new(
 		our_node_id: Uuid,
 		fullmesh: Arc<FullMeshPeeringStrategy>,
-		ring: watch::Receiver<Arc<Ring>>,
+		layout: Arc<RwLock<LayoutHelper>>,
 		rpc_timeout: Option<Duration>,
 	) -> Self {
 		let metrics = RpcMetrics::new();
@ -108,7 +107,7 @@ impl RpcHelper {
 		Self(Arc::new(RpcHelperInner {
 			our_node_id,
 			fullmesh,
-			ring,
+			layout,
 			metrics,
 			rpc_timeout: rpc_timeout.unwrap_or(DEFAULT_TIMEOUT),
 		}))
@ -236,31 +235,19 @@ impl RpcHelper {
 		let quorum = strategy.rs_quorum.unwrap_or(to.len());
 		let tracer = opentelemetry::global::tracer("garage");
-		let span_name = if strategy.rs_interrupt_after_quorum {
+		let span_name = format!("Read RPC {} to {} of {}", endpoint.path(), quorum, to.len());
-			format!("RPC {} to {} of {}", endpoint.path(), quorum, to.len())
+
 		} else {
 			format!(
 				"RPC {} to {} (quorum {})",
 				endpoint.path(),
 				to.len(),
 				quorum
 			)
 		};
 		let mut span = tracer.start(span_name);
 		span.set_attribute(KeyValue::new("from", format!("{:?}", self.0.our_node_id)));
 		span.set_attribute(KeyValue::new("to", format!("{:?}", to)));
 		span.set_attribute(KeyValue::new("quorum", quorum as i64));
 		span.set_attribute(KeyValue::new(
 			"interrupt_after_quorum",
 			strategy.rs_interrupt_after_quorum.to_string(),
 		));
-		self.try_call_many_internal(endpoint, to, msg, strategy, quorum)
+		self.try_call_many_inner(endpoint, to, msg, strategy, quorum)
 			.with_context(Context::current_with_span(span))
 			.await
 	}
-	async fn try_call_many_internal<M, N, H, S>(
+	async fn try_call_many_inner<M, N, H, S>(
 		&self,
 		endpoint: &Arc<Endpoint<M, H>>,
 		to: &[Uuid],
@ -274,12 +261,20 @@ impl RpcHelper {
 		H: StreamingEndpointHandler<M> + 'static,
 		S: Send + 'static,
 	{
-		let msg = msg.into_req().map_err(netapp::error::Error::from)?;
+		// Once quorum is reached, other requests don't matter.
 		// What we do here is only send the required number of requests
 		// to reach a quorum, priorizing nodes with the lowest latency.
 		// When there are errors, we start new requests to compensate.
 		// Reorder requests to priorize closeness / low latency
 		let request_order = self.request_order(to);
 		let send_all_at_once = strategy.rs_send_all_at_once.unwrap_or(false);
 		// Build future for each request
 		// They are not started now: they are added below in a FuturesUnordered
 		// object that will take care of polling them (see below)
-		let requests = to.iter().cloned().map(|to| {
+		let msg = msg.into_req().map_err(netapp::error::Error::from)?;
 		let mut requests = request_order.into_iter().map(|to| {
 			let self2 = self.clone();
 			let msg = msg.clone();
 			let endpoint2 = endpoint.clone();
@ -292,108 +287,59 @@ impl RpcHelper {
 		let mut successes = vec![];
 		let mut errors = vec![];
 		if strategy.rs_interrupt_after_quorum {
 			// Case 1: once quorum is reached, other requests don't matter.
 			// What we do here is only send the required number of requests
 			// to reach a quorum, priorizing nodes with the lowest latency.
 			// When there are errors, we start new requests to compensate.
 			// Reorder requests to priorize closeness / low latency
 			let request_order = self.request_order(to);
 			let mut ord_requests = vec![(); request_order.len()]
 				.into_iter()
 				.map(|_| None)
 				.collect::<Vec<_>>();
 			for (to, fut) in requests {
 				let i = request_order.iter().position(|x| *x == to).unwrap();
 				ord_requests[i] = Some((to, fut));
 			}
 			// Make an iterator to take requests in their sorted order
 			let mut requests = ord_requests.into_iter().map(Option::unwrap);
 		// resp_stream will contain all of the requests that are currently in flight.
 		// (for the moment none, they will be added in the loop below)
 		let mut resp_stream = FuturesUnordered::new();
 		// Do some requests and collect results
-			'request_loop: while successes.len() < quorum {
+		while successes.len() < quorum {
 			// If the current set of requests that are running is not enough to possibly
 			// reach quorum, start some new requests.
-				while successes.len() + resp_stream.len() < quorum {
+			while send_all_at_once || successes.len() + resp_stream.len() < quorum {
 				if let Some((req_to, fut)) = requests.next() {
 					let tracer = opentelemetry::global::tracer("garage");
 					let span = tracer.start(format!("RPC to {:?}", req_to));
-						resp_stream.push(tokio::spawn(
+					resp_stream.push(fut.with_context(Context::current_with_span(span)));
 							fut.with_context(Context::current_with_span(span)),
 						));
 				} else {
 						// If we have no request to add, we know that we won't ever
 						// reach quorum: bail out now.
 						break 'request_loop;
 					}
 				}
 				assert!(!resp_stream.is_empty()); // because of loop invariants
 				// Wait for one request to terminate
 				match resp_stream.next().await.unwrap().unwrap() {
 					Ok(msg) => {
 						successes.push(msg);
 					}
 					Err(e) => {
 						errors.push(e);
 					}
 				}
 			}
 		} else {
 			// Case 2: all of the requests need to be sent in all cases,
 			// and need to terminate. (this is the case for writes that
 			// must be spread to n nodes)
 			// Just start all the requests in parallel and return as soon
 			// as the quorum is reached.
 			let mut resp_stream = requests
 				.map(|(_, fut)| fut)
 				.collect::<FuturesUnordered<_>>();
 			while let Some(resp) = resp_stream.next().await {
 				match resp {
 					Ok(msg) => {
 						successes.push(msg);
 						if successes.len() >= quorum {
 					break;
 				}
 			}
 			if successes.len() + resp_stream.len() < quorum {
 				// We know we won't ever reach quorum
 				break;
 			}
 			// Wait for one request to terminate
 			match resp_stream.next().await.unwrap() {
 				Ok(msg) => {
 					successes.push(msg);
 				}
 				Err(e) => {
 					errors.push(e);
 				}
 			}
 		}
 			if !resp_stream.is_empty() {
 				// Continue remaining requests in background.
 				// Note: these requests can get interrupted on process shutdown,
 				// we must not count on them being executed for certain.
 				// For all background things that have to happen with certainty,
 				// they have to be put in a proper queue that is persisted to disk.
 				tokio::spawn(async move {
 					resp_stream.collect::<Vec<Result<_, _>>>().await;
 				});
 			}
 		}
 		if successes.len() >= quorum {
 			Ok(successes)
 		} else {
 			let errors = errors.iter().map(|e| format!("{}", e)).collect::<Vec<_>>();
-			Err(Error::Quorum(quorum, successes.len(), to.len(), errors))
+			Err(Error::Quorum(
 				quorum,
 				None,
 				successes.len(),
 				to.len(),
 				errors,
 			))
 		}
 	}
 	pub fn request_order(&self, nodes: &[Uuid]) -> Vec<Uuid> {
 		// Retrieve some status variables that we will use to sort requests
 		let peer_list = self.0.fullmesh.get_peer_list();
-		let ring: Arc<Ring> = self.0.ring.borrow().clone();
+		let layout = self.0.layout.read().unwrap();
-		let our_zone = match ring.layout.node_role(&self.0.our_node_id) {
+		let our_zone = match layout.current().node_role(&self.0.our_node_id) {
 			Some(pc) => &pc.zone,
 			None => "",
 		};
@ -407,7 +353,7 @@ impl RpcHelper {
 		let mut nodes = nodes
 			.iter()
 			.map(|to| {
-				let peer_zone = match ring.layout.node_role(to) {
+				let peer_zone = match layout.current().node_role(to) {
 					Some(pc) => &pc.zone,
 					None => "",
 				};
@ -433,4 +379,127 @@ impl RpcHelper {
 			.map(|(_, _, _, to)| to)
 			.collect::<Vec<_>>()
 	}
 	pub async fn try_write_many_sets<M, N, H, S>(
 		&self,
 		endpoint: &Arc<Endpoint<M, H>>,
 		to_sets: &[Vec<Uuid>],
 		msg: N,
 		strategy: RequestStrategy,
 	) -> Result<Vec<S>, Error>
 	where
 		M: Rpc<Response = Result<S, Error>> + 'static,
 		N: IntoReq<M>,
 		H: StreamingEndpointHandler<M> + 'static,
 		S: Send + 'static,
 	{
 		let quorum = strategy
 			.rs_quorum
 			.expect("internal error: missing quroum in try_write_many_sets");
 		let tracer = opentelemetry::global::tracer("garage");
 		let span_name = format!(
 			"Write RPC {} (quorum {} in {} sets)",
 			endpoint.path(),
 			quorum,
 			to_sets.len()
 		);
 		let mut span = tracer.start(span_name);
 		span.set_attribute(KeyValue::new("from", format!("{:?}", self.0.our_node_id)));
 		span.set_attribute(KeyValue::new("to", format!("{:?}", to_sets)));
 		span.set_attribute(KeyValue::new("quorum", quorum as i64));
 		self.try_write_many_sets_inner(endpoint, to_sets, msg, strategy, quorum)
 			.with_context(Context::current_with_span(span))
 			.await
 	}
 	async fn try_write_many_sets_inner<M, N, H, S>(
 		&self,
 		endpoint: &Arc<Endpoint<M, H>>,
 		to_sets: &[Vec<Uuid>],
 		msg: N,
 		strategy: RequestStrategy,
 		quorum: usize,
 	) -> Result<Vec<S>, Error>
 	where
 		M: Rpc<Response = Result<S, Error>> + 'static,
 		N: IntoReq<M>,
 		H: StreamingEndpointHandler<M> + 'static,
 		S: Send + 'static,
 	{
 		let msg = msg.into_req().map_err(netapp::error::Error::from)?;
 		let mut peers = HashMap::<Uuid, Vec<usize>>::new();
 		for (i, set) in to_sets.iter().enumerate() {
 			for peer in set.iter() {
 				peers.entry(*peer).or_default().push(i);
 			}
 		}
 		let requests = peers.iter().map(|(peer, _)| {
 			let self2 = self.clone();
 			let msg = msg.clone();
 			let endpoint2 = endpoint.clone();
 			let to = *peer;
 			let tracer = opentelemetry::global::tracer("garage");
 			let span = tracer.start(format!("RPC to {:?}", to));
 			let fut = async move { (to, self2.call(&endpoint2, to, msg, strategy).await) };
 			fut.with_context(Context::current_with_span(span))
 		});
 		let mut resp_stream = requests.collect::<FuturesUnordered<_>>();
 		let mut successes = vec![];
 		let mut errors = vec![];
 		let mut set_counters = vec![(0, 0); to_sets.len()];
 		while let Some((node, resp)) = resp_stream.next().await {
 			match resp {
 				Ok(msg) => {
 					for set in peers.get(&node).unwrap().iter() {
 						set_counters[*set].0 += 1;
 					}
 					successes.push(msg);
 				}
 				Err(e) => {
 					for set in peers.get(&node).unwrap().iter() {
 						set_counters[*set].1 += 1;
 					}
 					errors.push(e);
 				}
 			}
 			if set_counters.iter().all(|(ok_cnt, _)| *ok_cnt >= quorum) {
 				// Success
 				// Continue all other requets in background
 				tokio::spawn(async move {
 					resp_stream.collect::<Vec<(Uuid, Result<_, _>)>>().await;
 				});
 				return Ok(successes);
 			}
 			if set_counters
 				.iter()
 				.enumerate()
 				.any(|(i, (_, err_cnt))| err_cnt + quorum > to_sets[i].len())
 			{
 				// Too many errors in this set, we know we won't get a quorum
 				break;
 			}
 		}
 		// Failure, could not get quorum
 		let errors = errors.iter().map(|e| format!("{}", e)).collect::<Vec<_>>();
 		Err(Error::Quorum(
 			quorum,
 			Some(to_sets.len()),
 			successes.len(),
 			peers.len(),
 			errors,
 		))
 	}
 }
--- a/src/rpc/system.rs
+++ b/src/rpc/system.rs
@ -4,7 +4,7 @@ use std::io::{Read, Write};
 use std::net::{IpAddr, SocketAddr};
 use std::path::{Path, PathBuf};
 use std::sync::atomic::Ordering;
-use std::sync::{Arc, RwLock};
+use std::sync::{Arc, RwLock, RwLockReadGuard};
 use std::time::{Duration, Instant};
 use arc_swap::ArcSwap;
@ -13,8 +13,7 @@ use futures::join;
 use serde::{Deserialize, Serialize};
 use sodiumoxide::crypto::sign::ed25519;
 use tokio::select;
-use tokio::sync::watch;
+use tokio::sync::{watch, Notify};
 use tokio::sync::Mutex;
 use netapp::endpoint::{Endpoint, EndpointHandler};
 use netapp::message::*;
@ -34,9 +33,10 @@ use garage_util::time::*;
 use crate::consul::ConsulDiscovery;
 #[cfg(feature = "kubernetes-discovery")]
 use crate::kubernetes::*;
-use crate::layout::*;
+use crate::layout::{
 	self, manager::LayoutManager, LayoutDigest, LayoutHelper, LayoutHistory, NodeRoleV,
 };
 use crate::replication_mode::*;
 use crate::ring::*;
 use crate::rpc_helper::*;
 use crate::system_metrics::*;
@ -47,10 +47,10 @@ const STATUS_EXCHANGE_INTERVAL: Duration = Duration::from_secs(10);
 /// Version tag used for version check upon Netapp connection.
 /// Cluster nodes with different version tags are deemed
 /// incompatible and will refuse to connect.
-pub const GARAGE_VERSION_TAG: u64 = 0x6761726167650008; // garage 0x0008
+pub const GARAGE_VERSION_TAG: u64 = 0x676172616765000A; // garage 0x000A
 /// RPC endpoint used for calls related to membership
-pub const SYSTEM_RPC_PATH: &str = "garage_rpc/membership.rs/SystemRpc";
+pub const SYSTEM_RPC_PATH: &str = "garage_rpc/system.rs/SystemRpc";
 /// RPC messages related to membership
 #[derive(Debug, Serialize, Deserialize, Clone)]
@ -59,17 +59,22 @@ pub enum SystemRpc {
 	Ok,
 	/// Request to connect to a specific node (in <pubkey>@<host>:<port> format)
 	Connect(String),
 	/// Ask other node its cluster layout. Answered with AdvertiseClusterLayout
 	PullClusterLayout,
 	/// Advertise Garage status. Answered with another AdvertiseStatus.
 	/// Exchanged with every node on a regular basis.
 	AdvertiseStatus(NodeStatus),
 	/// Advertisement of cluster layout. Sent spontanously or in response to PullClusterLayout
 	AdvertiseClusterLayout(ClusterLayout),
 	/// Get known nodes states
 	GetKnownNodes,
 	/// Return known nodes
 	ReturnKnownNodes(Vec<KnownNodeInfo>),
 	/// Ask other node its cluster layout. Answered with AdvertiseClusterLayout
 	PullClusterLayout,
 	/// Advertisement of cluster layout. Sent spontanously or in response to PullClusterLayout
 	AdvertiseClusterLayout(LayoutHistory),
 	/// Ask other node its cluster layout update trackers.
 	PullClusterLayoutTrackers,
 	/// Advertisement of cluster layout update trackers.
 	AdvertiseClusterLayoutTrackers(layout::UpdateTrackers),
 }
 impl Rpc for SystemRpc {
@ -85,7 +90,6 @@ pub struct System {
 	/// The id of this node
 	pub id: Uuid,
 	persist_cluster_layout: Persister<ClusterLayout>,
 	persist_peer_list: Persister<PeerList>,
 	local_status: ArcSwap<NodeStatus>,
@ -93,9 +97,8 @@ pub struct System {
 	pub netapp: Arc<NetApp>,
 	fullmesh: Arc<FullMeshPeeringStrategy>,
 	pub rpc: RpcHelper,
-	system_endpoint: Arc<Endpoint<SystemRpc, System>>,
+	pub(crate) system_endpoint: Arc<Endpoint<SystemRpc, System>>,
 	rpc_listen_addr: SocketAddr,
 	#[cfg(any(feature = "consul-discovery", feature = "kubernetes-discovery"))]
@ -107,15 +110,13 @@ pub struct System {
 	#[cfg(feature = "kubernetes-discovery")]
 	kubernetes_discovery: Option<KubernetesDiscoveryConfig>,
 	pub layout_manager: Arc<LayoutManager>,
 	metrics: SystemMetrics,
 	replication_mode: ReplicationMode,
 	replication_factor: usize,
 	/// The ring
 	pub ring: watch::Receiver<Arc<Ring>>,
 	update_ring: Mutex<watch::Sender<Arc<Ring>>>,
 	/// Path to metadata directory
 	pub metadata_dir: PathBuf,
 	/// Path to data directory
@ -129,10 +130,9 @@ pub struct NodeStatus {
 	/// Replication factor configured on the node
 	pub replication_factor: usize,
-	/// Cluster layout version
+
-	pub cluster_layout_version: u64,
+	/// Cluster layout digest
-	/// Hash of cluster layout staging data
+	pub layout_digest: LayoutDigest,
 	pub cluster_layout_staging_hash: Hash,
 	/// Disk usage on partition containing metadata directory (tuple: `(avail, total)`)
 	#[serde(default)]
@ -248,8 +248,7 @@ impl System {
 		replication_mode: ReplicationMode,
 		config: &Config,
 	) -> Result<Arc<Self>, Error> {
-		let replication_factor = replication_mode.replication_factor();
+		// ---- setup netapp RPC protocol ----
 		let node_key =
 			gen_node_key(&config.metadata_dir).expect("Unable to read or generate node ID");
 		info!(
@ -257,82 +256,40 @@ impl System {
 			hex::encode(&node_key.public_key()[..8])
 		);
-		let persist_cluster_layout: Persister<ClusterLayout> =
+		let netapp = NetApp::new(GARAGE_VERSION_TAG, network_key, node_key);
-			Persister::new(&config.metadata_dir, "cluster_layout");
+		let system_endpoint = netapp.endpoint(SYSTEM_RPC_PATH.into());
 		let persist_peer_list = Persister::new(&config.metadata_dir, "peer_list");
-		let cluster_layout = match persist_cluster_layout.load() {
+		// ---- setup netapp public listener and full mesh peering strategy ----
-			Ok(x) => {
+		let rpc_public_addr = get_rpc_public_addr(config);
 				if x.replication_factor != replication_factor {
 					return Err(Error::Message(format!(
 						"Prevous cluster layout has replication factor {}, which is different than the one specified in the config file ({}). The previous cluster layout can be purged, if you know what you are doing, simply by deleting the `cluster_layout` file in your metadata directory.",
 						x.replication_factor,
 						replication_factor
 					)));
 				}
 				x
 			}
 			Err(e) => {
 				info!(
 					"No valid previous cluster layout stored ({}), starting fresh.",
 					e
 				);
 				ClusterLayout::new(replication_factor)
 			}
 		};
 		let metrics = SystemMetrics::new(replication_factor);
 		let mut local_status = NodeStatus::initial(replication_factor, &cluster_layout);
 		local_status.update_disk_usage(&config.metadata_dir, &config.data_dir, &metrics);
 		let ring = Ring::new(cluster_layout, replication_factor);
 		let (update_ring, ring) = watch::channel(Arc::new(ring));
 		let rpc_public_addr = match &config.rpc_public_addr {
 			Some(a_str) => {
 				use std::net::ToSocketAddrs;
 				match a_str.to_socket_addrs() {
 					Err(e) => {
 						error!(
 							"Cannot resolve rpc_public_addr {} from config file: {}.",
 							a_str, e
 						);
 						None
 					}
 					Ok(a) => {
 						let a = a.collect::<Vec<_>>();
 						if a.is_empty() {
 							error!("rpc_public_addr {} resolve to no known IP address", a_str);
 						}
 						if a.len() > 1 {
 							warn!("Multiple possible resolutions for rpc_public_addr: {:?}. Taking the first one.", a);
 						}
 						a.into_iter().next()
 					}
 				}
 			}
 			None => {
 				let addr =
 					get_default_ip().map(|ip| SocketAddr::new(ip, config.rpc_bind_addr.port()));
 				if let Some(a) = addr {
 					warn!("Using autodetected rpc_public_addr: {}. Consider specifying it explicitly in configuration file if possible.", a);
 				}
 				addr
 			}
 		};
 		if rpc_public_addr.is_none() {
 			warn!("This Garage node does not know its publicly reachable RPC address, this might hamper intra-cluster communication.");
 		}
 		let netapp = NetApp::new(GARAGE_VERSION_TAG, network_key, node_key);
 		let fullmesh = FullMeshPeeringStrategy::new(netapp.clone(), vec![], rpc_public_addr);
 		if let Some(ping_timeout) = config.rpc_ping_timeout_msec {
 			fullmesh.set_ping_timeout_millis(ping_timeout);
 		}
-		let system_endpoint = netapp.endpoint(SYSTEM_RPC_PATH.into());
+		let persist_peer_list = Persister::new(&config.metadata_dir, "peer_list");
 		// ---- setup cluster layout and layout manager ----
 		let replication_factor = replication_mode.replication_factor();
 		let layout_manager = LayoutManager::new(
 			config,
 			netapp.id,
 			system_endpoint.clone(),
 			fullmesh.clone(),
 			replication_factor,
 		)?;
 		// ---- set up metrics and status exchange ----
 		let metrics = SystemMetrics::new(replication_factor);
 		let mut local_status = NodeStatus::initial(replication_factor, &layout_manager);
 		local_status.update_disk_usage(&config.metadata_dir, &config.data_dir, &metrics);
 		// ---- if enabled, set up additionnal peer discovery methods ----
 		#[cfg(feature = "consul-discovery")]
 		let consul_discovery = match &config.consul_discovery {
 			Some(cfg) => Some(
@ -351,20 +308,14 @@ impl System {
 			warn!("Kubernetes discovery is not enabled in this build.");
 		}
 		// ---- done ----
 		let sys = Arc::new(System {
 			id: netapp.id.into(),
 			persist_cluster_layout,
 			persist_peer_list,
 			local_status: ArcSwap::new(Arc::new(local_status)),
 			node_status: RwLock::new(HashMap::new()),
 			netapp: netapp.clone(),
 			fullmesh: fullmesh.clone(),
 			rpc: RpcHelper::new(
 				netapp.id.into(),
 				fullmesh,
 				ring.clone(),
 				config.rpc_timeout_msec.map(Duration::from_millis),
 			),
 			system_endpoint,
 			replication_mode,
 			replication_factor,
@ -376,10 +327,9 @@ impl System {
 			consul_discovery,
 			#[cfg(feature = "kubernetes-discovery")]
 			kubernetes_discovery: config.kubernetes_discovery.clone(),
 			layout_manager,
 			metrics,
 			ring,
 			update_ring: Mutex::new(update_ring),
 			metadata_dir: config.metadata_dir.clone(),
 			data_dir: config.data_dir.clone(),
 		});
@ -399,6 +349,20 @@ impl System {
 		);
 	}
 	// ---- Public utilities / accessors ----
 	pub fn cluster_layout(&self) -> RwLockReadGuard<'_, LayoutHelper> {
 		self.layout_manager.layout()
 	}
 	pub fn layout_notify(&self) -> Arc<Notify> {
 		self.layout_manager.change_notify.clone()
 	}
 	pub fn rpc_helper(&self) -> &RpcHelper {
 		&self.layout_manager.rpc_helper
 	}
 	// ---- Administrative operations (directly available and
 	//      also available through RPC) ----
@ -425,18 +389,6 @@ impl System {
 		known_nodes
 	}
 	pub fn get_cluster_layout(&self) -> ClusterLayout {
 		self.ring.borrow().layout.clone()
 	}
 	pub async fn update_cluster_layout(
 		self: &Arc<Self>,
 		layout: &ClusterLayout,
 	) -> Result<(), Error> {
 		self.handle_advertise_cluster_layout(layout).await?;
 		Ok(())
 	}
 	pub async fn connect(&self, node: &str) -> Result<(), Error> {
 		let (pubkey, addrs) = parse_and_resolve_peer_addr_async(node)
 			.await
@ -466,7 +418,9 @@ impl System {
 	}
 	pub fn health(&self) -> ClusterHealth {
-		let ring: Arc<_> = self.ring.borrow().clone();
+		// TODO: adapt this function to take into account layout history
 		// when estimating cluster health, and not just use current layout
 		let quorum = self.replication_mode.write_quorum();
 		let replication_factor = self.replication_factor;
@ -477,8 +431,10 @@ impl System {
 			.collect::<HashMap<Uuid, _>>();
 		let connected_nodes = nodes.iter().filter(|(_, n)| n.is_up).count();
-		let storage_nodes = ring
+		let layout = self.cluster_layout(); // acquires a rwlock
-			.layout
+
 		let storage_nodes = layout
 			.current()
 			.roles
 			.items()
 			.iter()
@ -489,13 +445,12 @@ impl System {
 			.filter(|(x, _, _)| nodes.get(x).map(|n| n.is_up).unwrap_or(false))
 			.count();
-		let partitions = ring.partitions();
+		let partitions = layout.current().partitions().collect::<Vec<_>>();
 		let partitions_n_up = partitions
 			.iter()
 			.map(|(_, h)| {
-				let pn = ring.get_nodes(h, ring.replication_factor);
+				let pn = layout.current().nodes_of(h, replication_factor);
-				pn.iter()
+				pn.filter(|x| nodes.get(x).map(|n| n.is_up).unwrap_or(false))
 					.filter(|x| nodes.get(x).map(|n| n.is_up).unwrap_or(false))
 					.count()
 			})
 			.collect::<Vec<usize>>();
@ -582,22 +537,10 @@ impl System {
 		}
 	}
 	/// Save network configuration to disc
 	async fn save_cluster_layout(&self) -> Result<(), Error> {
 		let ring: Arc<Ring> = self.ring.borrow().clone();
 		self.persist_cluster_layout
 			.save_async(&ring.layout)
 			.await
 			.expect("Cannot save current cluster layout");
 		Ok(())
 	}
 	fn update_local_status(&self) {
 		let mut new_si: NodeStatus = self.local_status.load().as_ref().clone();
-		let ring = self.ring.borrow();
+		new_si.layout_digest = self.layout_manager.layout().digest();
 		new_si.cluster_layout_version = ring.layout.version;
 		new_si.cluster_layout_staging_hash = ring.layout.staging_hash;
 		new_si.update_disk_usage(&self.metadata_dir, &self.data_dir, &self.metrics);
@ -611,11 +554,6 @@ impl System {
 		Ok(SystemRpc::Ok)
 	}
 	fn handle_pull_cluster_layout(&self) -> SystemRpc {
 		let ring = self.ring.borrow().clone();
 		SystemRpc::AdvertiseClusterLayout(ring.layout.clone())
 	}
 	fn handle_get_known_nodes(&self) -> SystemRpc {
 		let known_nodes = self.get_known_nodes();
 		SystemRpc::ReturnKnownNodes(known_nodes)
@ -635,11 +573,8 @@ impl System {
 			std::process::exit(1);
 		}
-		if info.cluster_layout_version > local_info.cluster_layout_version
+		self.layout_manager
-			|| info.cluster_layout_staging_hash != local_info.cluster_layout_staging_hash
+			.handle_advertise_status(from, &info.layout_digest);
 		{
 			tokio::spawn(self.clone().pull_cluster_layout(from));
 		}
 		self.node_status
 			.write()
@ -649,57 +584,6 @@ impl System {
 		Ok(SystemRpc::Ok)
 	}
 	async fn handle_advertise_cluster_layout(
 		self: &Arc<Self>,
 		adv: &ClusterLayout,
 	) -> Result<SystemRpc, Error> {
 		if adv.replication_factor != self.replication_factor {
 			let msg = format!(
 				"Received a cluster layout from another node with replication factor {}, which is different from what we have in our configuration ({}). Discarding the cluster layout we received.",
 				adv.replication_factor,
 				self.replication_factor
 			);
 			error!("{}", msg);
 			return Err(Error::Message(msg));
 		}
 		let update_ring = self.update_ring.lock().await;
 		let mut layout: ClusterLayout = self.ring.borrow().layout.clone();
 		let prev_layout_check = layout.check().is_ok();
 		if layout.merge(adv) {
 			if prev_layout_check && layout.check().is_err() {
 				error!("New cluster layout is invalid, discarding.");
 				return Err(Error::Message(
 					"New cluster layout is invalid, discarding.".into(),
 				));
 			}
 			let ring = Ring::new(layout.clone(), self.replication_factor);
 			update_ring.send(Arc::new(ring))?;
 			drop(update_ring);
 			let self2 = self.clone();
 			tokio::spawn(async move {
 				if let Err(e) = self2
 					.rpc
 					.broadcast(
 						&self2.system_endpoint,
 						SystemRpc::AdvertiseClusterLayout(layout),
 						RequestStrategy::with_priority(PRIO_HIGH),
 					)
 					.await
 				{
 					warn!("Error while broadcasting new cluster layout: {}", e);
 				}
 			});
 			self.save_cluster_layout().await?;
 		}
 		Ok(SystemRpc::Ok)
 	}
 	async fn status_exchange_loop(&self, mut stop_signal: watch::Receiver<bool>) {
 		while !*stop_signal.borrow() {
 			let restart_at = Instant::now() + STATUS_EXCHANGE_INTERVAL;
@ -707,7 +591,7 @@ impl System {
 			self.update_local_status();
 			let local_status: NodeStatus = self.local_status.load().as_ref().clone();
 			let _ = self
-				.rpc
+				.rpc_helper()
 				.broadcast(
 					&self.system_endpoint,
 					SystemRpc::AdvertiseStatus(local_status),
@ -725,9 +609,9 @@ impl System {
 	async fn discovery_loop(self: &Arc<Self>, mut stop_signal: watch::Receiver<bool>) {
 		while !*stop_signal.borrow() {
-			let not_configured = self.ring.borrow().layout.check().is_err();
+			let not_configured = self.cluster_layout().check().is_err();
 			let no_peers = self.fullmesh.get_peer_list().len() < self.replication_factor;
-			let expected_n_nodes = self.ring.borrow().layout.num_nodes();
+			let expected_n_nodes = self.cluster_layout().all_nodes().len();
 			let bad_peers = self
 				.fullmesh
 				.get_peer_list()
@ -832,48 +716,47 @@ impl System {
 			.save_async(&PeerList(peer_list))
 			.await
 	}
 	async fn pull_cluster_layout(self: Arc<Self>, peer: Uuid) {
 		let resp = self
 			.rpc
 			.call(
 				&self.system_endpoint,
 				peer,
 				SystemRpc::PullClusterLayout,
 				RequestStrategy::with_priority(PRIO_HIGH),
 			)
 			.await;
 		if let Ok(SystemRpc::AdvertiseClusterLayout(layout)) = resp {
 			let _: Result<_, _> = self.handle_advertise_cluster_layout(&layout).await;
 		}
 	}
 }
 #[async_trait]
 impl EndpointHandler<SystemRpc> for System {
 	async fn handle(self: &Arc<Self>, msg: &SystemRpc, from: NodeID) -> Result<SystemRpc, Error> {
 		match msg {
 			// ---- system functions -> System ----
 			SystemRpc::Connect(node) => self.handle_connect(node).await,
 			SystemRpc::PullClusterLayout => Ok(self.handle_pull_cluster_layout()),
 			SystemRpc::AdvertiseStatus(adv) => self.handle_advertise_status(from.into(), adv).await,
 			SystemRpc::AdvertiseClusterLayout(adv) => {
 				self.clone().handle_advertise_cluster_layout(adv).await
 			}
 			SystemRpc::GetKnownNodes => Ok(self.handle_get_known_nodes()),
 			// ---- layout functions -> LayoutManager ----
 			SystemRpc::PullClusterLayout => Ok(self.layout_manager.handle_pull_cluster_layout()),
 			SystemRpc::AdvertiseClusterLayout(adv) => {
 				self.layout_manager
 					.handle_advertise_cluster_layout(adv)
 					.await
 			}
 			SystemRpc::PullClusterLayoutTrackers => {
 				Ok(self.layout_manager.handle_pull_cluster_layout_trackers())
 			}
 			SystemRpc::AdvertiseClusterLayoutTrackers(adv) => {
 				self.layout_manager
 					.handle_advertise_cluster_layout_trackers(adv)
 					.await
 			}
 			// ---- other -> Error ----
 			m => Err(Error::unexpected_rpc_message(m)),
 		}
 	}
 }
 impl NodeStatus {
-	fn initial(replication_factor: usize, layout: &ClusterLayout) -> Self {
+	fn initial(replication_factor: usize, layout_manager: &LayoutManager) -> Self {
 		NodeStatus {
 			hostname: gethostname::gethostname()
 				.into_string()
 				.unwrap_or_else(|_| "<invalid utf-8>".to_string()),
 			replication_factor,
-			cluster_layout_version: layout.version,
+			layout_digest: layout_manager.layout().digest(),
 			cluster_layout_staging_hash: layout.staging_hash,
 			meta_disk_avail: None,
 			data_disk_avail: None,
 		}
@ -883,8 +766,7 @@ impl NodeStatus {
 		NodeStatus {
 			hostname: "?".to_string(),
 			replication_factor: 0,
-			cluster_layout_version: 0,
+			layout_digest: Default::default(),
 			cluster_layout_staging_hash: Hash::from([0u8; 32]),
 			meta_disk_avail: None,
 			data_disk_avail: None,
 		}
@ -963,6 +845,40 @@ fn get_default_ip() -> Option<IpAddr> {
 		.map(|a| a.ip())
 }
 fn get_rpc_public_addr(config: &Config) -> Option<SocketAddr> {
 	match &config.rpc_public_addr {
 		Some(a_str) => {
 			use std::net::ToSocketAddrs;
 			match a_str.to_socket_addrs() {
 				Err(e) => {
 					error!(
 						"Cannot resolve rpc_public_addr {} from config file: {}.",
 						a_str, e
 					);
 					None
 				}
 				Ok(a) => {
 					let a = a.collect::<Vec<_>>();
 					if a.is_empty() {
 						error!("rpc_public_addr {} resolve to no known IP address", a_str);
 					}
 					if a.len() > 1 {
 						warn!("Multiple possible resolutions for rpc_public_addr: {:?}. Taking the first one.", a);
 					}
 					a.into_iter().next()
 				}
 			}
 		}
 		None => {
 			let addr = get_default_ip().map(|ip| SocketAddr::new(ip, config.rpc_bind_addr.port()));
 			if let Some(a) = addr {
 				warn!("Using autodetected rpc_public_addr: {}. Consider specifying it explicitly in configuration file if possible.", a);
 			}
 			addr
 		}
 	}
 }
 async fn resolve_peers(peers: &[String]) -> Vec<(NodeID, SocketAddr)> {
 	let mut ret = vec![];
--- a/src/table/data.rs
+++ b/src/table/data.rs
@ -254,7 +254,8 @@ impl<F: TableSchema, R: TableReplication> TableData<F, R> {
 				// of the GC algorithm, as in all cases GC is suspended if
 				// any node of the partition is unavailable.
 				let pk_hash = Hash::try_from(&tree_key[..32]).unwrap();
-				let nodes = self.replication.write_nodes(&pk_hash);
+				// TODO: this probably breaks when the layout changes
 				let nodes = self.replication.storage_nodes(&pk_hash);
 				if nodes.first() == Some(&self.system.id) {
 					GcTodoEntry::new(tree_key, new_bytes_hash).save(&self.gc_todo)?;
 				}
--- a/src/table/gc.rs
+++ b/src/table/gc.rs
@ -152,7 +152,7 @@ impl<F: TableSchema, R: TableReplication> TableGc<F, R> {
 		let mut partitions = HashMap::new();
 		for entry in entries {
 			let pkh = Hash::try_from(&entry.key[..32]).unwrap();
-			let mut nodes = self.data.replication.write_nodes(&pkh);
+			let mut nodes = self.data.replication.storage_nodes(&pkh);
 			nodes.retain(|x| *x != self.system.id);
 			nodes.sort();
@ -227,10 +227,10 @@ impl<F: TableSchema, R: TableReplication> TableGc<F, R> {
 		// GC'ing is not a critical function of the system, so it's not a big
 		// deal if we can't do it right now.
 		self.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
-				&nodes[..],
+				&nodes,
 				GcRpc::Update(updates),
 				RequestStrategy::with_priority(PRIO_BACKGROUND).with_quorum(nodes.len()),
 			)
@ -248,10 +248,10 @@ impl<F: TableSchema, R: TableReplication> TableGc<F, R> {
 		// it means that the garbage collection wasn't completed and has
 		// to be retried later.
 		self.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
-				&nodes[..],
+				&nodes,
 				GcRpc::DeleteIfEqualHash(deletes),
 				RequestStrategy::with_priority(PRIO_BACKGROUND).with_quorum(nodes.len()),
 			)
--- a/src/table/merkle.rs
+++ b/src/table/merkle.rs
@ -13,7 +13,7 @@ use garage_util::data::*;
 use garage_util::encode::{nonversioned_decode, nonversioned_encode};
 use garage_util::error::Error;
-use garage_rpc::ring::*;
+use garage_rpc::layout::*;
 use crate::data::*;
 use crate::replication::*;
--- a/src/table/replication/fullcopy.rs
+++ b/src/table/replication/fullcopy.rs
@ -1,15 +1,23 @@
 use std::iter::FromIterator;
 use std::sync::Arc;
-use garage_rpc::ring::*;
+use garage_rpc::layout::*;
 use garage_rpc::system::System;
 use garage_util::data::*;
 use crate::replication::*;
 // TODO: find a way to track layout changes for this as well
 // The hard thing is that this data is stored also on gateway nodes,
 // whereas sharded data is stored only on non-Gateway nodes (storage nodes)
 // Also we want to be more tolerant to failures of gateways so we don't
 // want to do too much holding back of data when progress of gateway
 // nodes is not reported in the layout history's ack/sync/sync_ack maps.
 /// Full replication schema: all nodes store everything
 /// Writes are disseminated in an epidemic manner in the network
 /// Advantage: do all reads locally, extremely fast
 /// Inconvenient: only suitable to reasonably small tables
 /// Inconvenient: if some writes fail, nodes will read outdated data
 #[derive(Clone)]
 pub struct TableFullReplication {
 	/// The membership manager of this node
@ -19,6 +27,13 @@ pub struct TableFullReplication {
 }
 impl TableReplication for TableFullReplication {
 	type WriteSets = Vec<Vec<Uuid>>;
 	fn storage_nodes(&self, _hash: &Hash) -> Vec<Uuid> {
 		let layout = self.system.cluster_layout();
 		layout.current().all_nodes().to_vec()
 	}
 	fn read_nodes(&self, _hash: &Hash) -> Vec<Uuid> {
 		vec![self.system.id]
 	}
@ -26,12 +41,11 @@ impl TableReplication for TableFullReplication {
 		1
 	}
-	fn write_nodes(&self, _hash: &Hash) -> Vec<Uuid> {
+	fn write_sets(&self, hash: &Hash) -> Self::WriteSets {
-		let ring = self.system.ring.borrow();
+		vec![self.storage_nodes(hash)]
 		ring.layout.node_ids().to_vec()
 	}
 	fn write_quorum(&self) -> usize {
-		let nmembers = self.system.ring.borrow().layout.node_ids().len();
+		let nmembers = self.system.cluster_layout().current().all_nodes().len();
 		if nmembers > self.max_faults {
 			nmembers - self.max_faults
 		} else {
@ -45,7 +59,18 @@ impl TableReplication for TableFullReplication {
 	fn partition_of(&self, _hash: &Hash) -> Partition {
 		0u16
 	}
-	fn partitions(&self) -> Vec<(Partition, Hash)> {
+
-		vec![(0u16, [0u8; 32].into())]
+	fn sync_partitions(&self) -> SyncPartitions {
 		let layout = self.system.cluster_layout();
 		let layout_version = layout.current().version;
 		SyncPartitions {
 			layout_version,
 			partitions: vec![SyncPartition {
 				partition: 0u16,
 				first_hash: [0u8; 32].into(),
 				last_hash: [0xff; 32].into(),
 				storage_nodes: Vec::from_iter(layout.current().all_nodes().to_vec()),
 			}],
 		}
 	}
 }
--- a/src/table/replication/parameters.rs
+++ b/src/table/replication/parameters.rs
@ -1,25 +1,44 @@
-use garage_rpc::ring::*;
+use garage_rpc::layout::*;
 use garage_util::data::*;
 /// Trait to describe how a table shall be replicated
 pub trait TableReplication: Send + Sync + 'static {
 	type WriteSets: AsRef<Vec<Vec<Uuid>>> + Send + Sync + 'static;
 	// See examples in table_sharded.rs and table_fullcopy.rs
 	// To understand various replication methods
 	/// The entire list of all nodes that store a partition
 	fn storage_nodes(&self, hash: &Hash) -> Vec<Uuid>;
 	/// Which nodes to send read requests to
 	fn read_nodes(&self, hash: &Hash) -> Vec<Uuid>;
 	/// Responses needed to consider a read succesfull
 	fn read_quorum(&self) -> usize;
 	/// Which nodes to send writes to
-	fn write_nodes(&self, hash: &Hash) -> Vec<Uuid>;
+	fn write_sets(&self, hash: &Hash) -> Self::WriteSets;
-	/// Responses needed to consider a write succesfull
+	/// Responses needed to consider a write succesfull in each set
 	fn write_quorum(&self) -> usize;
 	fn max_write_errors(&self) -> usize;
 	// Accessing partitions, for Merkle tree & sync
 	/// Get partition for data with given hash
 	fn partition_of(&self, hash: &Hash) -> Partition;
-	/// List of existing partitions
+	/// List of partitions and nodes to sync with in current layout
-	fn partitions(&self) -> Vec<(Partition, Hash)>;
+	fn sync_partitions(&self) -> SyncPartitions;
 }
 #[derive(Debug)]
 pub struct SyncPartitions {
 	pub layout_version: u64,
 	pub partitions: Vec<SyncPartition>,
 }
 #[derive(Debug)]
 pub struct SyncPartition {
 	pub partition: Partition,
 	pub first_hash: Hash,
 	pub last_hash: Hash,
 	pub storage_nodes: Vec<Uuid>,
 }
--- a/src/table/replication/sharded.rs
+++ b/src/table/replication/sharded.rs
@ -1,6 +1,6 @@
 use std::sync::Arc;
-use garage_rpc::ring::*;
+use garage_rpc::layout::*;
 use garage_rpc::system::System;
 use garage_util::data::*;
@ -25,17 +25,21 @@ pub struct TableShardedReplication {
 }
 impl TableReplication for TableShardedReplication {
 	type WriteSets = WriteLock<Vec<Vec<Uuid>>>;
 	fn storage_nodes(&self, hash: &Hash) -> Vec<Uuid> {
 		self.system.cluster_layout().storage_nodes_of(hash)
 	}
 	fn read_nodes(&self, hash: &Hash) -> Vec<Uuid> {
-		let ring = self.system.ring.borrow();
+		self.system.cluster_layout().read_nodes_of(hash)
 		ring.get_nodes(hash, self.replication_factor)
 	}
 	fn read_quorum(&self) -> usize {
 		self.read_quorum
 	}
-	fn write_nodes(&self, hash: &Hash) -> Vec<Uuid> {
+	fn write_sets(&self, hash: &Hash) -> Self::WriteSets {
-		let ring = self.system.ring.borrow();
+		self.system.layout_manager.write_sets_of(hash)
 		ring.get_nodes(hash, self.replication_factor)
 	}
 	fn write_quorum(&self) -> usize {
 		self.write_quorum
@ -45,9 +49,38 @@ impl TableReplication for TableShardedReplication {
 	}
 	fn partition_of(&self, hash: &Hash) -> Partition {
-		self.system.ring.borrow().partition_of(hash)
+		self.system.cluster_layout().current().partition_of(hash)
 	}
 	fn sync_partitions(&self) -> SyncPartitions {
 		let layout = self.system.cluster_layout();
 		let layout_version = layout.all_ack();
 		let mut partitions = layout
 			.current()
 			.partitions()
 			.map(|(partition, first_hash)| {
 				let storage_nodes = layout.storage_nodes_of(&first_hash);
 				SyncPartition {
 					partition,
 					first_hash,
 					last_hash: [0u8; 32].into(), // filled in just after
 					storage_nodes,
 				}
 			})
 			.collect::<Vec<_>>();
 		for i in 0..partitions.len() {
 			partitions[i].last_hash = if i + 1 < partitions.len() {
 				partitions[i + 1].first_hash
 			} else {
 				[0xFFu8; 32].into()
 			};
 		}
 		SyncPartitions {
 			layout_version,
 			partitions,
 		}
 	fn partitions(&self) -> Vec<(Partition, Hash)> {
 		self.system.ring.borrow().partitions()
 	}
 }
--- a/src/table/sync.rs
+++ b/src/table/sync.rs
@ -6,18 +6,18 @@ use arc_swap::ArcSwapOption;
 use async_trait::async_trait;
 use futures_util::stream::*;
 use opentelemetry::KeyValue;
-use rand::Rng;
+use rand::prelude::*;
 use serde::{Deserialize, Serialize};
 use serde_bytes::ByteBuf;
 use tokio::select;
-use tokio::sync::{mpsc, watch};
+use tokio::sync::{mpsc, watch, Notify};
 use garage_util::background::*;
 use garage_util::data::*;
 use garage_util::encode::{debug_serialize, nonversioned_encode};
 use garage_util::error::{Error, OkOrMessage};
-use garage_rpc::ring::*;
+use garage_rpc::layout::*;
 use garage_rpc::system::System;
 use garage_rpc::*;
@ -52,16 +52,6 @@ impl Rpc for SyncRpc {
 	type Response = Result<SyncRpc, Error>;
 }
 #[derive(Debug, Clone)]
 struct TodoPartition {
 	partition: Partition,
 	begin: Hash,
 	end: Hash,
 	// Are we a node that stores this partition or not?
 	retain: bool,
 }
 impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 	pub(crate) fn new(
 		system: Arc<System>,
@ -91,10 +81,10 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 		bg.spawn_worker(SyncWorker {
 			syncer: self.clone(),
-			ring_recv: self.system.ring.clone(),
+			layout_notify: self.system.layout_notify(),
-			ring: self.system.ring.borrow().clone(),
+			layout_versions: self.system.cluster_layout().sync_versions(),
 			add_full_sync_rx,
-			todo: vec![],
+			todo: None,
 			next_full_sync: Instant::now() + Duration::from_secs(20),
 		});
 	}
@ -112,31 +102,26 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 	async fn sync_partition(
 		self: &Arc<Self>,
-		partition: &TodoPartition,
+		partition: &SyncPartition,
 		must_exit: &mut watch::Receiver<bool>,
 	) -> Result<(), Error> {
 		if partition.retain {
 		let my_id = self.system.id;
 		let retain = partition.storage_nodes.contains(&my_id);
-			let nodes = self
+		if retain {
 				.data
 				.replication
 				.write_nodes(&partition.begin)
 				.into_iter()
 				.filter(|node| *node != my_id)
 				.collect::<Vec<_>>();
 			debug!(
 				"({}) Syncing {:?} with {:?}...",
 				F::TABLE_NAME,
 				partition,
-				nodes
+				partition.storage_nodes
 			);
-			let mut sync_futures = nodes
+			let mut sync_futures = partition
 				.storage_nodes
 				.iter()
 				.filter(|node| **node != my_id)
 				.map(|node| {
 					self.clone()
-						.do_sync_with(partition.clone(), *node, must_exit.clone())
+						.do_sync_with(&partition, *node, must_exit.clone())
 				})
 				.collect::<FuturesUnordered<_>>();
@ -147,14 +132,14 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 					warn!("({}) Sync error: {}", F::TABLE_NAME, e);
 				}
 			}
-			if n_errors > self.data.replication.max_write_errors() {
+			if n_errors > 0 {
 				return Err(Error::Message(format!(
-					"Sync failed with too many nodes (should have been: {:?}).",
+					"Sync failed with {} nodes.",
-					nodes
+					n_errors
 				)));
 			}
 		} else {
-			self.offload_partition(&partition.begin, &partition.end, must_exit)
+			self.offload_partition(&partition.first_hash, &partition.last_hash, must_exit)
 				.await?;
 		}
@ -188,12 +173,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 			}
 			if !items.is_empty() {
-				let nodes = self
+				let nodes = self.data.replication.storage_nodes(begin);
 					.data
 					.replication
 					.write_nodes(begin)
 					.into_iter()
 					.collect::<Vec<_>>();
 				if nodes.contains(&self.system.id) {
 					warn!(
 						"({}) Interrupting offload as partitions seem to have changed",
@ -217,7 +197,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 					end,
 					counter
 				);
-				self.offload_items(&items, &nodes[..]).await?;
+				self.offload_items(&items, &nodes).await?;
 			} else {
 				break;
 			}
@ -244,7 +224,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 		}
 		self.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
 				nodes,
@ -285,7 +265,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 	async fn do_sync_with(
 		self: Arc<Self>,
-		partition: TodoPartition,
+		partition: &SyncPartition,
 		who: Uuid,
 		must_exit: watch::Receiver<bool>,
 	) -> Result<(), Error> {
@ -305,7 +285,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 		// If so, do nothing.
 		let root_resp = self
 			.system
-			.rpc
+			.rpc_helper()
 			.call(
 				&self.endpoint,
 				who,
@ -361,7 +341,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 					// and compare it with local node
 					let remote_node = match self
 						.system
-						.rpc
+						.rpc_helper()
 						.call(
 							&self.endpoint,
 							who,
@ -437,7 +417,7 @@ impl<F: TableSchema, R: TableReplication> TableSyncer<F, R> {
 		let rpc_resp = self
 			.system
-			.rpc
+			.rpc_helper()
 			.call(
 				&self.endpoint,
 				who,
@ -492,76 +472,44 @@ impl<F: TableSchema, R: TableReplication> EndpointHandler<SyncRpc> for TableSync
 struct SyncWorker<F: TableSchema, R: TableReplication> {
 	syncer: Arc<TableSyncer<F, R>>,
-	ring_recv: watch::Receiver<Arc<Ring>>,
+
-	ring: Arc<Ring>,
+	layout_notify: Arc<Notify>,
 	layout_versions: (u64, u64, u64),
 	add_full_sync_rx: mpsc::UnboundedReceiver<()>,
 	todo: Vec<TodoPartition>,
 	next_full_sync: Instant,
 	todo: Option<SyncPartitions>,
 }
 impl<F: TableSchema, R: TableReplication> SyncWorker<F, R> {
 	fn check_add_full_sync(&mut self) {
 		let layout_versions = self.syncer.system.cluster_layout().sync_versions();
 		if layout_versions != self.layout_versions {
 			self.layout_versions = layout_versions;
 			info!(
 				"({}) Layout versions changed (max={}, ack={}, min stored={}), adding full sync to syncer todo list",
 				F::TABLE_NAME,
 				layout_versions.0,
 				layout_versions.1,
 				layout_versions.2
 			);
 			self.add_full_sync();
 		}
 	}
 	fn add_full_sync(&mut self) {
-		let system = &self.syncer.system;
+		let mut partitions = self.syncer.data.replication.sync_partitions();
-		let data = &self.syncer.data;
+		info!(
-
+			"{}: Adding full sync for ack layout version {}",
-		let my_id = system.id;
+			F::TABLE_NAME,
-
+			partitions.layout_version
-		self.todo.clear();
+		);
 		let partitions = data.replication.partitions();
 		for i in 0..partitions.len() {
 			let begin = partitions[i].1;
 			let end = if i + 1 < partitions.len() {
 				partitions[i + 1].1
 			} else {
 				[0xFFu8; 32].into()
 			};
 			let nodes = data.replication.write_nodes(&begin);
 			let retain = nodes.contains(&my_id);
 			if !retain {
 				// Check if we have some data to send, otherwise skip
 				match data.store.range(begin..end) {
 					Ok(mut iter) => {
 						if iter.next().is_none() {
 							continue;
 						}
 					}
 					Err(e) => {
 						warn!("DB error in add_full_sync: {}", e);
 						continue;
 					}
 				}
 			}
 			self.todo.push(TodoPartition {
 				partition: partitions[i].0,
 				begin,
 				end,
 				retain,
 			});
 		}
 		partitions.partitions.shuffle(&mut thread_rng());
 		self.todo = Some(partitions);
 		self.next_full_sync = Instant::now() + ANTI_ENTROPY_INTERVAL;
 	}
 	fn pop_task(&mut self) -> Option<TodoPartition> {
 		if self.todo.is_empty() {
 			return None;
 		}
 		let i = rand::thread_rng().gen_range(0..self.todo.len());
 		if i == self.todo.len() - 1 {
 			self.todo.pop()
 		} else {
 			let replacement = self.todo.pop().unwrap();
 			let ret = std::mem::replace(&mut self.todo[i], replacement);
 			Some(ret)
 		}
 	}
 }
 #[async_trait]
@ -572,14 +520,48 @@ impl<F: TableSchema, R: TableReplication> Worker for SyncWorker<F, R> {
 	fn status(&self) -> WorkerStatus {
 		WorkerStatus {
-			queue_length: Some(self.todo.len() as u64),
+			queue_length: Some(self.todo.as_ref().map(|x| x.partitions.len()).unwrap_or(0) as u64),
 			..Default::default()
 		}
 	}
 	async fn work(&mut self, must_exit: &mut watch::Receiver<bool>) -> Result<WorkerState, Error> {
-		if let Some(partition) = self.pop_task() {
+		self.check_add_full_sync();
-			self.syncer.sync_partition(&partition, must_exit).await?;
+
 		if let Some(todo) = &mut self.todo {
 			let partition = todo.partitions.pop().unwrap();
 			// process partition
 			if let Err(e) = self.syncer.sync_partition(&partition, must_exit).await {
 				error!(
 					"{}: Failed to sync partition {:?}: {}",
 					F::TABLE_NAME,
 					partition,
 					e
 				);
 				// if error, put partition back at the other side of the queue,
 				// so that other partitions will be tried in the meantime
 				todo.partitions.insert(0, partition);
 				// TODO: returning an error here will cause the background job worker
 				// to delay this task for some time, but maybe we don't want to
 				// delay it if there are lots of failures from nodes that are gone
 				// (we also don't want zero delays as that will cause lots of useless retries)
 				return Err(e);
 			}
 			if todo.partitions.is_empty() {
 				info!(
 					"{}: Completed full sync for ack layout version {}",
 					F::TABLE_NAME,
 					todo.layout_version
 				);
 				self.syncer
 					.system
 					.layout_manager
 					.sync_table_until(F::TABLE_NAME, todo.layout_version);
 				self.todo = None;
 			}
 			Ok(WorkerState::Busy)
 		} else {
 			Ok(WorkerState::Idle)
@ -593,22 +575,16 @@ impl<F: TableSchema, R: TableReplication> Worker for SyncWorker<F, R> {
 					self.add_full_sync();
 				}
 			},
-			_ = self.ring_recv.changed() => {
+			_ = self.layout_notify.notified() => {
-				let new_ring = self.ring_recv.borrow();
+				self.check_add_full_sync();
 				if !Arc::ptr_eq(&new_ring, &self.ring) {
 					self.ring = new_ring.clone();
 					drop(new_ring);
 					debug!("({}) Ring changed, adding full sync to syncer todo list", F::TABLE_NAME);
 					self.add_full_sync();
 				}
 			},
 			_ = tokio::time::sleep_until(self.next_full_sync.into()) => {
 				self.add_full_sync();
 			}
 		}
-		match self.todo.is_empty() {
+		match self.todo.is_some() {
-			false => WorkerState::Busy,
+			true => WorkerState::Busy,
-			true => WorkerState::Idle,
+			false => WorkerState::Idle,
 		}
 	}
 }
--- a/src/table/table.rs
+++ b/src/table/table.rs
@ -80,6 +80,8 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 		let syncer = TableSyncer::new(system.clone(), data.clone(), merkle_updater.clone());
 		let gc = TableGc::new(system.clone(), data.clone());
 		system.layout_manager.add_table(F::TABLE_NAME);
 		let table = Arc::new(Self {
 			system,
 			data,
@ -117,16 +119,16 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 	async fn insert_internal(&self, e: &F::E) -> Result<(), Error> {
 		let hash = e.partition_key().hash();
-		let who = self.data.replication.write_nodes(&hash);
+		let who = self.data.replication.write_sets(&hash);
 		let e_enc = Arc::new(ByteBuf::from(e.encode()?));
 		let rpc = TableRpc::<F>::Update(vec![e_enc]);
 		self.system
-			.rpc
+			.rpc_helper()
-			.try_call_many(
+			.try_write_many_sets(
 				&self.endpoint,
-				&who[..],
+				who.as_ref(),
 				rpc,
 				RequestStrategy::with_priority(PRIO_NORMAL)
 					.with_quorum(self.data.replication.write_quorum()),
@ -141,7 +143,7 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 		self.data.queue_insert(tx, e)
 	}
-	pub async fn insert_many<I, IE>(&self, entries: I) -> Result<(), Error>
+	pub async fn insert_many<I, IE>(self: &Arc<Self>, entries: I) -> Result<(), Error>
 	where
 		I: IntoIterator<Item = IE> + Send + Sync,
 		IE: Borrow<F::E> + Send + Sync,
@ -159,51 +161,149 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 		Ok(())
 	}
-	async fn insert_many_internal<I, IE>(&self, entries: I) -> Result<(), Error>
+	async fn insert_many_internal<I, IE>(self: &Arc<Self>, entries: I) -> Result<(), Error>
 	where
 		I: IntoIterator<Item = IE> + Send + Sync,
 		IE: Borrow<F::E> + Send + Sync,
 	{
-		let mut call_list: HashMap<_, Vec<_>> = HashMap::new();
+		// The different items will have to be stored on possibly different nodes.
 		// We will here batch all items into a single request for each concerned
 		// node, with all of the entries it must store within that request.
 		// Each entry has to be saved to a specific list of "write sets", i.e. a set
 		// of node within wich a quorum must be achieved. In normal operation, there
 		// is a single write set which corresponds to the quorum in the current
 		// cluster layout, but when the layout is updated, multiple write sets might
 		// have to be handled at once. Here, since we are sending many entries, we
 		// will have to handle many write sets in all cases. The algorihtm is thus
 		// to send one request to each node with all the items it must save,
 		// and keep track of the OK responses within each write set: if for all sets
 		// a quorum of nodes has answered OK, then the insert has succeeded and
 		// consistency properties (read-after-write) are preserved.
 		// Some code here might feel redundant with RpcHelper::try_write_many_sets,
 		// but I think deduplicating could lead to more spaghetti instead of
 		// improving the readability, so I'm leaving as is.
 		let quorum = self.data.replication.write_quorum();
 		// Serialize all entries and compute the write sets for each of them.
 		// In the case of sharded table replication, this also takes an "ack lock"
 		// to the layout manager to avoid ack'ing newer versions which are not
 		// taken into account by writes in progress (the ack can happen later, once
 		// all writes that didn't take the new layout into account are finished).
 		// These locks are released when entries_vec is dropped, i.e. when this
 		// function returns.
 		let mut entries_vec = Vec::new();
 		for entry in entries.into_iter() {
 			let entry = entry.borrow();
 			let hash = entry.partition_key().hash();
-			let who = self.data.replication.write_nodes(&hash);
+			let write_sets = self.data.replication.write_sets(&hash);
 			let e_enc = Arc::new(ByteBuf::from(entry.encode()?));
-			for node in who {
+			entries_vec.push((write_sets, e_enc));
-				call_list.entry(node).or_default().push(e_enc.clone());
+		}
 		// Compute a deduplicated list of all of the write sets,
 		// and compute an index from each node to the position of the sets in which
 		// it takes part, to optimize the detection of a quorum.
 		let mut write_sets = entries_vec
 			.iter()
 			.map(|(wss, _)| wss.as_ref().iter().map(|ws| ws.as_slice()))
 			.flatten()
 			.collect::<Vec<&[Uuid]>>();
 		write_sets.sort();
 		write_sets.dedup();
 		let mut write_set_index = HashMap::<&Uuid, Vec<usize>>::new();
 		for (i, write_set) in write_sets.iter().enumerate() {
 			for node in write_set.iter() {
 				write_set_index.entry(node).or_default().push(i);
 			}
 		}
-		let call_futures = call_list.drain().map(|(node, entries)| async move {
+		// Build a map of all nodes to the entries that must be sent to that node.
 		let mut call_list: HashMap<Uuid, Vec<_>> = HashMap::new();
 		for (write_sets, entry_enc) in entries_vec.iter() {
 			for write_set in write_sets.as_ref().iter() {
 				for node in write_set.iter() {
 					call_list.entry(*node).or_default().push(entry_enc.clone())
 				}
 			}
 		}
 		// Build futures to actually perform each of the corresponding RPC calls
 		let call_count = call_list.len();
 		let call_futures = call_list.into_iter().map(|(node, entries)| {
 			let this = self.clone();
 			let tracer = opentelemetry::global::tracer("garage");
 			let span = tracer.start(format!("RPC to {:?}", node));
 			let fut = async move {
 				let rpc = TableRpc::<F>::Update(entries);
-
+				let resp = this
 			let resp = self
 					.system
-				.rpc
+					.rpc_helper()
 					.call(
-					&self.endpoint,
+						&this.endpoint,
 						node,
 						rpc,
-					RequestStrategy::with_priority(PRIO_NORMAL),
+						RequestStrategy::with_priority(PRIO_NORMAL).with_quorum(quorum),
 					)
-				.await?;
+					.await;
-			Ok::<_, Error>((node, resp))
+				(node, resp)
 			};
 			fut.with_context(Context::current_with_span(span))
 		});
 		// Run all requests in parallel thanks to FuturesUnordered, and collect results.
 		let mut resps = call_futures.collect::<FuturesUnordered<_>>();
 		let mut set_counters = vec![(0, 0); write_sets.len()];
 		let mut successes = 0;
 		let mut errors = vec![];
-		while let Some(resp) = resps.next().await {
+		while let Some((node, resp)) = resps.next().await {
-			if let Err(e) = resp {
+			match resp {
 				Ok(_) => {
 					successes += 1;
 					for set in write_set_index.get(&node).unwrap().iter() {
 						set_counters[*set].0 += 1;
 					}
 				}
 				Err(e) => {
 					errors.push(e);
 					for set in write_set_index.get(&node).unwrap().iter() {
 						set_counters[*set].1 += 1;
 					}
 				}
 		if errors.len() > self.data.replication.max_write_errors() {
 			Err(Error::Message("Too many errors".into()))
 		} else {
 			Ok(())
 			}
 			if set_counters.iter().all(|(ok_cnt, _)| *ok_cnt >= quorum) {
 				// Success
 				// Continue all other requests in background
 				tokio::spawn(async move {
 					resps.collect::<Vec<(Uuid, Result<_, _>)>>().await;
 				});
 				return Ok(());
 			}
 			if set_counters
 				.iter()
 				.enumerate()
 				.any(|(i, (_, err_cnt))| err_cnt + quorum > write_sets[i].len())
 			{
 				// Too many errors in this set, we know we won't get a quorum
 				break;
 			}
 		}
 		// Failure, could not get quorum within at least one set
 		let errors = errors.iter().map(|e| format!("{}", e)).collect::<Vec<_>>();
 		Err(Error::Quorum(
 			quorum,
 			Some(write_sets.len()),
 			successes,
 			call_count,
 			errors,
 		))
 	}
 	pub async fn get(
@ -236,14 +336,13 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 		let rpc = TableRpc::<F>::ReadEntry(partition_key.clone(), sort_key.clone());
 		let resps = self
 			.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
-				&who[..],
+				&who,
 				rpc,
 				RequestStrategy::with_priority(PRIO_NORMAL)
-					.with_quorum(self.data.replication.read_quorum())
+					.with_quorum(self.data.replication.read_quorum()),
 					.interrupt_after_quorum(true),
 			)
 			.await?;
@ -332,14 +431,13 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 		let resps = self
 			.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
-				&who[..],
+				&who,
 				rpc,
 				RequestStrategy::with_priority(PRIO_NORMAL)
-					.with_quorum(self.data.replication.read_quorum())
+					.with_quorum(self.data.replication.read_quorum()),
 					.interrupt_after_quorum(true),
 			)
 			.await?;
@ -411,7 +509,7 @@ impl<F: TableSchema, R: TableReplication> Table<F, R> {
 	async fn repair_on_read(&self, who: &[Uuid], what: F::E) -> Result<(), Error> {
 		let what_enc = Arc::new(ByteBuf::from(what.encode()?));
 		self.system
-			.rpc
+			.rpc_helper()
 			.try_call_many(
 				&self.endpoint,
 				who,
--- a/src/util/error.rs
+++ b/src/util/error.rs
@ -55,13 +55,14 @@ pub enum Error {
 	Timeout,
 	#[error(
-		display = "Could not reach quorum of {}. {} of {} request succeeded, others returned errors: {:?}",
+		display = "Could not reach quorum of {} (sets={:?}). {} of {} request succeeded, others returned errors: {:?}",
 		_0,
 		_1,
 		_2,
-		_3
+		_3,
 		_4
 	)]
-	Quorum(usize, usize, usize, Vec<String>),
+	Quorum(usize, Option<usize>, usize, usize, Vec<String>),
 	#[error(display = "Unexpected RPC message: {}", _0)]
 	UnexpectedRpcMessage(String),
Author	SHA1	Message	Date
Alex Auvolat	3ecd14b9f6	table: implement write sets for insert_many	2023-11-16 16:41:45 +01:00
Alex Auvolat	22f38808e7	rpc_helper: don't use tokio::spawn for individual requests	2023-11-16 16:34:01 +01:00
Alex Auvolat	707442f5de	layout: refactor digests and add "!=" assertions before epidemic bcast	2023-11-16 13:51:40 +01:00
Alex Auvolat	ad5c6f779f	layout: split helper in separate file; more precise difference tracking	2023-11-16 13:26:43 +01:00
Alex Auvolat	d4df03424f	layout: fix test	2023-11-15 15:56:57 +01:00
Alex Auvolat	33c8a489b0	layou: implement ack locking	2023-11-15 15:40:44 +01:00
Alex Auvolat	393c4d4515	layout: add helper for cached/external values to centralize recomputation	2023-11-15 14:20:50 +01:00
Alex Auvolat	65066c7064	layout: wip cache global mins	2023-11-15 13:28:30 +01:00
Alex Auvolat	acd49de9f9	rpc: fix write set quorums	2023-11-15 13:07:42 +01:00
Alex Auvolat	46007bf01d	integration test: print stdout and stderr on subcommand crash	2023-11-15 12:56:52 +01:00
Alex Auvolat	b3e729f4b8	layout history merge: rm invalid versions when valid versions are added	2023-11-15 12:15:58 +01:00
Alex Auvolat	7ef2c23120	layout: fix test	2023-11-14 15:45:01 +01:00
Alex Auvolat	90e1619b1e	table: take into account multiple write sets in inserts	2023-11-14 15:40:46 +01:00
Alex Auvolat	3b361d2959	layout: prepare for write sets	2023-11-14 14:28:16 +01:00
Alex Auvolat	866196750f	system: add todo wrt new layout	2023-11-14 13:36:58 +01:00
Alex Auvolat	83a11374ca	layout: fixes in schema	2023-11-14 13:29:26 +01:00
Alex Auvolat	1aab1f4e68	layout: refactoring of all_nodes	2023-11-14 13:12:32 +01:00
Alex Auvolat	8e292e06b3	layout: some refactoring of nongateway nodes	2023-11-14 12:48:38 +01:00
Alex Auvolat	9a491fa137	layout: fix test	2023-11-11 13:10:59 +01:00
Alex Auvolat	df24bb806d	layout/sync: fix bugs and add tracing	2023-11-11 12:44:27 +01:00
Alex Auvolat	ce89d1ddab	table sync: adapt to new layout history	2023-11-11 12:08:32 +01:00
Alex Auvolat	df36cf3099	layout: add helpers to LayoutHistory and prepare integration with Table	2023-11-09 16:32:31 +01:00
Alex Auvolat	9d95f6f704	layout: fix tracker bugs	2023-11-09 15:52:45 +01:00
Alex Auvolat	bad7cc812e	layout admin: add missing calls to update_hash	2023-11-09 15:42:10 +01:00
Alex Auvolat	03ebf18830	layout: begin managing the update tracker values	2023-11-09 15:31:59 +01:00
Alex Auvolat	94caf9c0c1	layout: separate code path for synchronizing update trackers only	2023-11-09 14:53:34 +01:00
Alex Auvolat	bfb1845fdc	layout: refactor to use a RwLock on LayoutHistory	2023-11-09 14:12:05 +01:00
Alex Auvolat	19ef1ec8e7	layout: more refactoring	2023-11-09 13:34:14 +01:00
Alex Auvolat	8a2b1dd422	wip: split out layout management from System into separate LayoutManager	2023-11-09 12:55:36 +01:00
Alex Auvolat	523d2ecb95	layout: use separate CRDT for staged layout changes	2023-11-09 11:19:43 +01:00
Alex Auvolat	1da0a5676e	bump garage protocol version tag to 0x000A (0.10)	2023-11-08 19:30:58 +01:00
Alex Auvolat	8dccee3ccf	cluster layout: adapt all uses of ClusterLayout to LayoutHistory	2023-11-08 19:28:36 +01:00
Alex Auvolat	fe9af1dcaa	WIP: garage_rpc: store layout version history	2023-11-08 17:49:06 +01:00
Alex Auvolat	4a9c94514f	avoid using layout_watch in System directly	2023-11-08 16:41:00 +01:00
Alex Auvolat	12d1dbfc6b	remove Ring and use ClusterLayout everywhere	2023-11-08 15:41:24 +01:00
Alex Auvolat	0962313ebd	garage_rpc: reorder functions in layout.rs	2023-11-08 13:13:04 +01:00