forked from Deuxfleurs/garage
Add explanations about quorums
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6 changed files with 66 additions and 27 deletions
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@ -684,20 +684,77 @@
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\end{frame}
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\begin{frame}
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\frametitle{Performance gains in practice}
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\begin{center}
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\includegraphics[width=.8\linewidth]{assets/endpoint-latency-dc.png}
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\end{center}
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\end{frame}
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\frametitle{Read-after-write consistency:}
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\textbf{Property:} If node $A$ did an operation $write(x)$ and received an OK response,\\
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\hspace{2cm} and node $B$ starts an operation $read()$ after $A$ received OK,\\
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\hspace{2cm} then $B$ will read a value $x' \sqsupseteq x$.
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\vspace{1em}
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\hspace{1em}
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\begin{minipage}{6.8cm}
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\textbf{Algorithm $write(x)$:}
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\begin{enumerate}
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\item Broadcast $write(x)$ to all nodes
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\item Wait for $k > n/2$ nodes to reply OK
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\item Return OK
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\end{enumerate}
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\end{minipage}
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\hfill
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\begin{minipage}{6.8cm}
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\vspace{1em}
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\textbf{Algorithm $read()$:}
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\begin{enumerate}
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\item Broadcast $read()$ to all nodes
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\item Wait for $k > n/2$ nodes to reply\\
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with values $x_1, \dots, x_k$
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\item Return $x_1 \sqcup \dots \sqcup x_k$
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\end{enumerate}
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\end{minipage}
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\hspace{1em}
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\vspace{2em}
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\textbf{Why does it work?} There is at least one node at the intersection between the two sets of nodes that replied to each request, that ``saw'' $x$ before the $read()$ started ($x_i \sqsupseteq x$).
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\end{frame}
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\begin{frame}
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\frametitle{An ever-increasing compatibility list}
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\begin{center}
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\includegraphics[width=.7\linewidth]{assets/compatibility.png}
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\end{center}
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\frametitle{Monotonical read consistency:}
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\textbf{Property:} If node $A$ did an operation $read()$ and received $x$ as a response,\\
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\hspace{2cm} and node $B$ starts an operation $read()$ after $A$ received $x$,\\
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\hspace{2cm} then $B$ will read a value $x' \sqsupseteq x$.
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\vspace{1em}
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\textbf{Algorithm $read()$:}
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\begin{enumerate}
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\item Broadcast $read()$ to all nodes
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\item Wait for $k > n/2$ nodes to reply with values $x_1, \dots, x_k$
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\item If $x_i \ne x_j$ for some nodes $i$ and $j$,\\
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\hspace{1cm}then call $write(x_1 \sqcup \dots \sqcup x_k)$ and wait for OK from $k' > n/2$ nodes
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\item Return $x_1 \sqcup \dots \sqcup x_k$
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\end{enumerate}
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\vspace{1em}
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This makes reads slower in some cases, and is \textbf{not implemented in Garage}.
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\end{frame}
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\begin{frame}
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\frametitle{Performance gains in practice}
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\begin{center}
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\includegraphics[width=.8\linewidth]{assets/endpoint-latency-dc.png}
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\end{center}
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\end{frame}
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\begin{frame}
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\frametitle{The hard parts we don't address (yet!)}
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\begin{itemize}
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\item Maintain consistency changes when nodes assigned to a partition change:\\
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\item TODO
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\end{itemize}
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\end{frame}
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\section{Going further than the S3 API}
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\begin{frame}
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\frametitle{Further plans for Garage}
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\begin{center}
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@ -728,24 +785,6 @@
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\end{center}
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\end{frame}
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\begin{frame}
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\frametitle{Aerogramme data model}
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\begin{center}
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\only<1>{\includegraphics[width=.4\linewidth]{assets/aerogramme_datatype.drawio.pdf}}%
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\only<2->{\includegraphics[width=.9\linewidth]{assets/aerogramme_keys.drawio.pdf}\vspace{1em}}%
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\end{center}
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\visible<3->{Aerogramme encrypts all stored values for privacy\\
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(Garage server administrators can't read your mail)}
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\end{frame}
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\begin{frame}
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\frametitle{Different deployment scenarios}
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\begin{center}
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\only<1>{\includegraphics[width=.9\linewidth]{assets/aerogramme_components1.drawio.pdf}}%
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\only<2>{\includegraphics[width=.9\linewidth]{assets/aerogramme_components2.drawio.pdf}}%
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\end{center}
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\end{frame}
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\begin{frame}
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\frametitle{A new model for building resilient software}
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\begin{itemize}
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