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+\nonstopmode
+\documentclass[aspectratio=169,xcolor={svgnames}]{beamer}
+\usepackage[utf8]{inputenc}
+% \usepackage[frenchb]{babel}
+\usepackage{amsmath}
+\usepackage{mathtools}
+\usepackage{breqn}
+\usepackage{multirow}
+\usetheme{boxes}
+\usepackage{graphicx}
+\usepackage{import}
+\usepackage{adjustbox}
+\usepackage[absolute,overlay]{textpos}
+%\useoutertheme[footline=authortitle,subsection=false]{miniframes}
+%\useoutertheme[footline=authorinstitute,subsection=false]{miniframes}
+\useoutertheme{infolines}
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+
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+
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+\setbeamertemplate{itemize item}{\color{ListOrange}$\blacktriangleright$}
+
+\definecolor{verygrey}{RGB}{70,70,70}
+\setbeamercolor{normal text}{fg=verygrey}
+
+
+\usepackage{tabu}
+\usepackage{multicol}
+\usepackage{vwcol}
+\usepackage{stmaryrd}
+\usepackage{graphicx}
+
+\usepackage[normalem]{ulem}
+
+\AtBeginSection[]{
+  \begin{frame}
+  \vfill
+  \centering
+  \begin{beamercolorbox}[sep=8pt,center,shadow=true,rounded=true]{title}
+    \usebeamerfont{title}\insertsectionhead\par%
+  \end{beamercolorbox}
+  \vfill
+  \end{frame}
+}
+
+\title{Garage}
+\author{Alex Auvolat, Deuxfleurs}
+\date{Capitoul, 2024-02-29}
+
+\begin{document}
+
+\begin{frame}
+	\centering
+	\includegraphics[width=.3\linewidth]{../../sticker/Garage.png}
+	\vspace{1em}
+
+	{\large\bf Alex Auvolat, Deuxfleurs Association}
+	\vspace{1em}
+
+	\url{https://garagehq.deuxfleurs.fr/}
+
+	Matrix channel: \texttt{\#garage:deuxfleurs.fr}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Who I am}
+	\begin{columns}[t]
+		\begin{column}{.2\textwidth}
+			\centering
+			\adjincludegraphics[width=.4\linewidth, valign=t]{../assets/alex.jpg}
+		\end{column}
+		\begin{column}{.6\textwidth}
+			\textbf{Alex Auvolat}\\
+			PhD; co-founder of Deuxfleurs
+		\end{column}
+		\begin{column}{.2\textwidth}
+			~
+		\end{column}
+	\end{columns}
+	\vspace{2em}
+
+	\begin{columns}[t]
+		\begin{column}{.2\textwidth}
+			\centering
+			\adjincludegraphics[width=.5\linewidth, valign=t]{../assets/logos/deuxfleurs.pdf}
+		\end{column}
+		\begin{column}{.6\textwidth}
+			\textbf{Deuxfleurs}\\
+			A non-profit self-hosting collective,\\
+			member of the CHATONS network
+		\end{column}
+		\begin{column}{.2\textwidth}
+			\centering
+			\adjincludegraphics[width=.7\linewidth, valign=t]{../assets/logos/logo_chatons.png}
+		\end{column}
+	\end{columns}
+
+\end{frame}
+
+\begin{frame}
+	\frametitle{Our objective at Deuxfleurs}
+	
+	\begin{center}
+		\textbf{Promote self-hosting and small-scale hosting\\
+			as an alternative to large cloud providers}
+	\end{center}
+	\vspace{2em}
+	\visible<2->{
+		Why is it hard?
+		\vspace{2em}
+		\begin{center}
+			\textbf{\underline{Resilience}}\\
+			{\footnotesize we want good uptime/availability with low supervision}
+		\end{center}
+	}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Our very low-tech infrastructure}
+
+	\only<1,3-6>{
+		\begin{itemize}
+			\item \textcolor<4->{gray}{Commodity hardware (e.g. old desktop PCs)\\
+				\vspace{.5em}
+				\visible<3->{{\footnotesize (can die at any time)}}}
+				\vspace{1.5em}
+			\item<4-> \textcolor<6->{gray}{Regular Internet (e.g. FTTB, FTTH) and power grid connections\\
+				\vspace{.5em}
+				\visible<5->{{\footnotesize (can be unavailable randomly)}}}
+				\vspace{1.5em}
+			\item<6-> \textbf{Geographical redundancy} (multi-site replication)
+		\end{itemize}
+	}
+	\only<2>{
+		\begin{center}
+			\includegraphics[width=.8\linewidth]{../assets/neptune.jpg}
+		\end{center}
+	}
+	\only<7>{
+		\begin{center}
+			\includegraphics[width=.8\linewidth]{../assets/inframap_jdll2023.pdf}
+		\end{center}
+	}
+\end{frame}
+
+\begin{frame}
+	\frametitle{How to make this happen}
+	\begin{center}
+		\only<1>{\includegraphics[width=.8\linewidth]{../assets/intro/slide1.png}}%
+		\only<2>{\includegraphics[width=.8\linewidth]{../assets/intro/slide2.png}}%
+		\only<3>{\includegraphics[width=.8\linewidth]{../assets/intro/slide3.png}}%
+	\end{center}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Distributed file systems are slow}
+	File systems are complex, for example:
+	\vspace{1em}
+	\begin{itemize}
+		\item Concurrent modification by several processes
+			\vspace{1em}
+		\item Folder hierarchies
+			\vspace{1em}
+		\item Other requirements of the POSIX spec (e.g.~locks)
+	\end{itemize}
+	\vspace{1em}
+	Coordination in a distributed system is costly
+
+	\vspace{1em}
+	Costs explode with commodity hardware / Internet connections\\
+	{\small (we experienced this!)}
+\end{frame}
+
+\begin{frame}
+	\frametitle{A simpler solution: object storage}
+	Only two operations:
+	\vspace{1em}
+	\begin{itemize}
+		\item Put an object at a key
+			\vspace{1em}
+		\item Retrieve an object from its key
+	\end{itemize}
+	\vspace{1em}
+	{\footnotesize (and a few others)}
+
+	\vspace{1em}
+	Sufficient for many applications!
+\end{frame}
+
+\begin{frame}
+	\frametitle{A simpler solution: object storage}
+		\begin{center}
+			\includegraphics[height=6em]{../assets/logos/Amazon-S3.jpg}
+			\hspace{3em}
+			\visible<2->{\includegraphics[height=5em]{../assets/logos/minio.png}}
+			\hspace{3em}
+			\visible<3>{\includegraphics[height=6em]{../../logo/garage_hires_crop.png}}
+		\end{center}
+		\vspace{1em}
+	S3: a de-facto standard, many compatible applications
+
+	\vspace{1em}
+	\visible<2->{MinIO is self-hostable but not suited for geo-distributed deployments}
+
+	\vspace{1em}
+	\visible<3->{\textbf{Garage is a self-hosted drop-in replacement for the Amazon S3 object store}}
+\end{frame}
+
+% --------- BASED ON CRDTS ----------
+
+\section{Principle 1: based on CRDTs}
+
+\begin{frame}
+	\frametitle{CRDTs / weak consistency instead of consensus}
+
+	\underline{Internally, Garage uses only CRDTs} (conflict-free replicated data types)
+
+	\vspace{2em}
+	Why not Raft, Paxos, ...? Issues of consensus algorithms:
+
+	\vspace{1em}
+	\begin{itemize}
+		\item<2-> \textbf{Software complexity}
+			\vspace{1em}
+		\item<3-> \textbf{Performance issues:}
+			\vspace{.5em}
+			\begin{itemize}
+				\item<4-> The leader is a \textbf{bottleneck} for all requests\\
+					\vspace{.5em}
+				\item<5-> \textbf{Sensitive to higher latency} between nodes
+					\vspace{.5em}
+				\item<6-> \textbf{Takes time to reconverge} when disrupted (e.g. node going down)
+			\end{itemize}
+	\end{itemize}
+\end{frame}
+
+\begin{frame}
+	\frametitle{The data model of object storage}
+	Object storage is basically a \textbf{key-value store}:
+	\vspace{.5em}
+
+	{\scriptsize
+		\begin{center}
+		\begin{tabular}{|l|p{7cm}|}
+			\hline
+			\textbf{Key: file path + name} & \textbf{Value: file data + metadata} \\
+			\hline
+			\hline
+			\texttt{index.html} &
+				\texttt{Content-Type: text/html; charset=utf-8} \newline
+				\texttt{Content-Length: 24929} \newline
+				\texttt{<binary blob>} \\ 
+			\hline
+			\texttt{img/logo.svg} &
+				\texttt{Content-Type: text/svg+xml} \newline
+				\texttt{Content-Length: 13429} \newline
+				\texttt{<binary blob>} \\ 
+			\hline
+			\texttt{download/index.html} &
+				\texttt{Content-Type: text/html; charset=utf-8} \newline
+				\texttt{Content-Length: 26563} \newline
+				\texttt{<binary blob>} \\ 
+			\hline
+		\end{tabular}
+		\end{center}
+		}
+
+	\vspace{.5em}
+	\begin{itemize}
+		\item<2-> Maps well to CRDT data types
+		\item<3> Read-after-write consistency with quorums
+	\end{itemize}
+\end{frame}
+
+
+\begin{frame}
+	\frametitle{Performance gains in practice}
+	\begin{center}
+		\includegraphics[width=.8\linewidth]{../assets/perf/endpoint_latency_0.7_0.8_minio.png}
+	\end{center}
+\end{frame}
+
+% --------- GEO-DISTRIBUTED MODEL ----------
+
+\section{Principle 2: geo-distributed data model}
+
+\begin{frame}
+	\frametitle{Key-value stores, upgraded: the Dynamo model}
+	\textbf{Two keys:}
+	\begin{itemize}
+		\item Partition key: used to divide data into partitions {\small (a.k.a.~shards)}
+		\item Sort key: used to identify items inside a partition
+	\end{itemize}
+
+	\vspace{1em}
+
+	\begin{center}
+	\begin{tabular}{|l|l|p{3cm}|}
+		\hline
+		\textbf{Partition key: bucket} & \textbf{Sort key: filename} & \textbf{Value} \\
+		\hline
+		\hline
+		\texttt{website} & \texttt{index.html} & (file data) \\
+		\hline
+		\texttt{website} & \texttt{img/logo.svg} & (file data) \\
+		\hline
+		\texttt{website} & \texttt{download/index.html} & (file data) \\
+		\hline
+		\hline
+		\texttt{backup} & \texttt{borg/index.2822} & (file data) \\
+		\hline
+		\texttt{backup} & \texttt{borg/data/2/2329} & (file data) \\
+		\hline
+		\texttt{backup} & \texttt{borg/data/2/2680} & (file data) \\
+		\hline
+		\hline
+		\texttt{private} & \texttt{qq3a2nbe1qjq0ebbvo6ocsp6co} & (file data) \\
+		\hline
+	\end{tabular}
+	\end{center}
+\end{frame}
+
+
+\begin{frame}
+	\frametitle{Layout computation}
+	\begin{overprint}
+		\onslide<1>
+		\begin{center}
+			\includegraphics[width=\linewidth, trim=0 0 0 -4cm]{../assets/screenshots/garage_status_0.9_prod_zonehl.png}
+		\end{center}
+		\onslide<2>
+		\begin{center}
+			\includegraphics[width=.7\linewidth]{../assets/map.png}
+		\end{center}
+	\end{overprint}
+	\vspace{1em}
+	Garage stores replicas on different zones when possible
+\end{frame}
+
+\begin{frame}
+	\frametitle{What a "layout" is}
+		\textbf{A layout is a precomputed index table:}
+		\vspace{1em}
+
+		{\footnotesize
+			\begin{center}
+			\begin{tabular}{|l|l|l|l|}
+				\hline
+				\textbf{Partition} & \textbf{Node 1} & \textbf{Node 2} & \textbf{Node 3} \\
+				\hline
+				\hline
+				Partition 0 & df-ymk (bespin) & Abricot (scorpio) & Courgette (neptune) \\
+				\hline
+				Partition 1 & Ananas (scorpio) & Courgette (neptune) & df-ykl (bespin) \\
+				\hline
+				Partition 2 & df-ymf (bespin) & Celeri (neptune) & Abricot (scorpio) \\
+				\hline
+				\hspace{1em}$\vdots$ & \hspace{1em}$\vdots$ & \hspace{1em}$\vdots$ & \hspace{1em}$\vdots$ \\
+				\hline
+				Partition 255 & Concombre (neptune) & df-ykl (bespin) & Abricot (scorpio) \\
+				\hline
+			\end{tabular}
+			\end{center}
+		}
+
+	\vspace{2em}
+	\visible<2->{
+		The index table is built centrally using an optimal algorithm,\\
+		then propagated to all nodes
+	}
+
+	\vspace{1em}
+	\visible<3->{
+		\footnotesize
+		Oulamara, M., \& Auvolat, A. (2023). \emph{An algorithm for geo-distributed and redundant storage in Garage}.\\ arXiv preprint arXiv:2302.13798.
+	}
+\end{frame}
+
+
+\begin{frame}
+	\frametitle{The relationship between \emph{partition} and \emph{partition key}}
+	\begin{center}
+	\begin{tabular}{|l|l|l|l|}
+		\hline
+		\textbf{Partition key} & \textbf{Partition} & \textbf{Sort key} & \textbf{Value} \\
+		\hline
+		\hline
+		\texttt{website} & Partition 12 & \texttt{index.html} & (file data) \\
+		\hline
+		\texttt{website} & Partition 12 & \texttt{img/logo.svg} & (file data) \\
+		\hline
+		\texttt{website} & Partition 12 &\texttt{download/index.html} & (file data) \\
+		\hline
+		\hline
+		\texttt{backup} & Partition 42 & \texttt{borg/index.2822} & (file data) \\
+		\hline
+		\texttt{backup} & Partition 42 & \texttt{borg/data/2/2329} & (file data) \\
+		\hline
+		\texttt{backup} & Partition 42 & \texttt{borg/data/2/2680} & (file data) \\
+		\hline
+		\hline
+		\texttt{private} & Partition 42 & \texttt{qq3a2nbe1qjq0ebbvo6ocsp6co} & (file data) \\
+		\hline
+	\end{tabular}
+	\end{center}
+	\vspace{1em}
+	\textbf{To read or write an item:} hash partition key
+	\\ \hspace{5cm} $\to$ determine partition number (first 8 bits)
+	\\ \hspace{5cm} $\to$ find associated nodes
+\end{frame}
+
+\begin{frame}
+	\frametitle{Garage's internal data structures}
+	\centering
+	\includegraphics[width=.75\columnwidth]{../assets/garage_tables.pdf}
+\end{frame}
+
+% ---------- OPERATING GARAGE ---------
+
+\section{Operating Garage clusters}
+
+\begin{frame}
+	\frametitle{Operating Garage}
+	\begin{center}
+		\only<1-2>{
+			\includegraphics[width=.9\linewidth]{../assets/screenshots/garage_status_0.10.png}
+			\\\vspace{1em}
+			\visible<2>{\includegraphics[width=.9\linewidth]{../assets/screenshots/garage_status_unhealthy_0.10.png}}
+		}
+	\end{center}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Background synchronization}
+	\begin{center}
+		\includegraphics[width=.6\linewidth]{../assets/garage_sync.drawio.pdf}
+	\end{center}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Digging deeper}
+	\begin{center}
+		\only<1>{\includegraphics[width=.9\linewidth]{../assets/screenshots/garage_stats_0.10.png}}
+		\only<2>{\includegraphics[width=.5\linewidth]{../assets/screenshots/garage_worker_list_0.10.png}}
+		\only<3>{\includegraphics[width=.6\linewidth]{../assets/screenshots/garage_worker_param_0.10.png}}
+	\end{center}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Monitoring with Prometheus + Grafana}
+	\begin{center}
+		\includegraphics[width=.9\linewidth]{../assets/screenshots/grafana_dashboard.png}
+	\end{center}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Debugging with traces}
+	\begin{center}
+		\includegraphics[width=.8\linewidth]{../assets/screenshots/jaeger_listobjects.png}
+	\end{center}
+\end{frame}
+
+% ---------- SCALING GARAGE ---------
+
+\section{Scaling Garage clusters}
+
+\begin{frame}
+	\frametitle{Potential limitations and bottlenecks}
+	\begin{itemize}
+		\item Global:
+			\begin{itemize}
+				\item Max. $\sim$100 nodes per cluster (excluding gateways)
+			\end{itemize}
+			\vspace{1em}
+		\item Metadata:
+			\begin{itemize}
+				\item One big bucket = bottleneck, object list on 3 nodes only
+			\end{itemize}
+			\vspace{1em}
+		\item Block manager:
+			\begin{itemize}
+				\item Lots of small files on disk
+				\item Processing the resync queue can be slow
+			\end{itemize}
+	\end{itemize}
+\end{frame}
+
+\begin{frame}
+	\frametitle{Deployment advice for very large clusters}
+	\begin{itemize}
+		\item Metadata storage:
+			\begin{itemize}
+				\item ZFS mirror (x2) on fast NVMe
+				\item Use LMDB storage engine
+			\end{itemize}
+			\vspace{.5em}
+		\item Data block storage:
+			\begin{itemize}
+				\item Use Garage's native multi-HDD support
+				\item XFS on individual drives
+				\item Increase block size (1MB $\to$ 10MB, requires more RAM and good networking)
+				\item Tune \texttt{resync-tranquility} and \texttt{resync-worker-count} dynamically
+			\end{itemize}
+			\vspace{.5em}
+		\item Other :
+			\begin{itemize}
+				\item Split data over several buckets
+				\item Use less than 100 storage nodes
+				\item Use gateway nodes
+			\end{itemize}
+			\vspace{.5em}
+	\end{itemize}
+	Our deployments: $< 10$ TB. Some people have done more!
+\end{frame}
+
+
+% ======================================== END
+% ======================================== END
+% ======================================== END
+
+\begin{frame}
+	\frametitle{Where to find us}
+	\begin{center}
+			\includegraphics[width=.25\linewidth]{../../logo/garage_hires.png}\\
+			\vspace{-1em}
+		\url{https://garagehq.deuxfleurs.fr/}\\
+		\url{mailto:garagehq@deuxfleurs.fr}\\
+		\texttt{\#garage:deuxfleurs.fr} on Matrix
+
+		\vspace{1.5em}
+			\includegraphics[width=.06\linewidth]{../assets/logos/rust_logo.png}
+			\includegraphics[width=.13\linewidth]{../assets/logos/AGPLv3_Logo.png}
+	\end{center}
+\end{frame}
+
+\end{document}
+
+%% vim: set ts=4 sw=4 tw=0 noet spelllang=en :