|
|
<!doctype html><html lang="en" class="no-js"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width,initial-scale=1"> <meta name="description" content="mergerfs - a featureful union filesystem"> <link rel="canonical" href="https://trapexit.github.io/mergerfs/usage_patterns/"> <link rel="prev" href="../tooling/"> <link rel="next" href="../faq/reliability_and_scalability/"> <link rel="icon" href="../assets/images/favicon.png"> <meta name="generator" content="mkdocs-1.6.1, mkdocs-material-9.5.50"> <title>Usage Patterns - mergerfs</title> <link rel="stylesheet" href="../assets/stylesheets/main.a40c8224.min.css"> <link rel="stylesheet" href="../assets/stylesheets/palette.06af60db.min.css">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin> <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto:300,300i,400,400i,700,700i%7CRoboto+Mono:400,400i,700,700i&display=fallback"> <style>:root{--md-text-font:"Roboto";--md-code-font:"Roboto Mono"}</style> <script>__md_scope=new URL("..",location),__md_hash=e=>[...e].reduce(((e,_)=>(e<<5)-e+_.charCodeAt(0)),0),__md_get=(e,_=localStorage,t=__md_scope)=>JSON.parse(_.getItem(t.pathname+"."+e)),__md_set=(e,_,t=localStorage,a=__md_scope)=>{try{t.setItem(a.pathname+"."+e,JSON.stringify(_))}catch(e){}}</script>
</head> <body dir="ltr" data-md-color-scheme="default" data-md-color-primary="indigo" data-md-color-accent="indigo"> <input class="md-toggle" data-md-toggle="drawer" type="checkbox" id="__drawer" autocomplete="off"> <input class="md-toggle" data-md-toggle="search" type="checkbox" id="__search" autocomplete="off"> <label class="md-overlay" for="__drawer"></label> <div data-md-component="skip"> <a href="#usage-patterns" class="md-skip"> Skip to content </a> </div> <div data-md-component="announce"> </div>
<header class="md-header md-header--shadow" data-md-component="header"> <nav class="md-header__inner md-grid" aria-label="Header"> <a href=".." title="mergerfs" class="md-header__button md-logo" aria-label="mergerfs" data-md-component="logo"> <img src="../logo.jpeg" alt="logo">
</a> <label class="md-header__button md-icon" for="__drawer"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M3 6h18v2H3zm0 5h18v2H3zm0 5h18v2H3z"/></svg> </label> <div class="md-header__title" data-md-component="header-title"> <div class="md-header__ellipsis"> <div class="md-header__topic"> <span class="md-ellipsis"> mergerfs </span> </div> <div class="md-header__topic" data-md-component="header-topic"> <span class="md-ellipsis"> Usage Patterns </span> </div> </div> </div> <form class="md-header__option" data-md-component="palette"> <input class="md-option" data-md-color-media="(prefers-color-scheme)" data-md-color-scheme="default" data-md-color-primary="indigo" data-md-color-accent="indigo" aria-label="Switch to light mode" type="radio" name="__palette" id="__palette_0"> <label class="md-header__button md-icon" title="Switch to light mode" for="__palette_1" hidden> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="m14.3 16-.7-2h-3.2l-.7 2H7.8L11 7h2l3.2 9zM20 8.69V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12zm-9.15 3.96h2.3L12 9z"/></svg> </label> <input class="md-option" data-md-color-media="(prefers-color-scheme: light)" data-md-color-scheme="default" data-md-color-primary="indigo" data-md-color-accent="indigo" aria-label="Switch to dark mode" type="radio" name="__palette" id="__palette_1"> <label class="md-header__button md-icon" title="Switch to dark mode" for="__palette_2" hidden> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M12 8a4 4 0 0 0-4 4 4 4 0 0 0 4 4 4 4 0 0 0 4-4 4 4 0 0 0-4-4m0 10a6 6 0 0 1-6-6 6 6 0 0 1 6-6 6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> <input class="md-option" data-md-color-media="(prefers-color-scheme: dark)" data-md-color-scheme="slate" data-md-color-primary="indigo" data-md-color-accent="indigo" aria-label="Switch to system preference" type="radio" name="__palette" id="__palette_2"> <label class="md-header__button md-icon" title="Switch to system preference" for="__palette_0" hidden> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M12 18c-.89 0-1.74-.2-2.5-.55C11.56 16.5 13 14.42 13 12s-1.44-4.5-3.5-5.45C10.26 6.2 11.11 6 12 6a6 6 0 0 1 6 6 6 6 0 0 1-6 6m8-9.31V4h-4.69L12 .69 8.69 4H4v4.69L.69 12 4 15.31V20h4.69L12 23.31 15.31 20H20v-4.69L23.31 12z"/></svg> </label> </form> <script>var palette=__md_get("__palette");if(palette&&palette.color){if("(prefers-color-scheme)"===palette.color.media){var media=matchMedia("(prefers-color-scheme: light)"),input=document.querySelector(media.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");palette.color.media=input.getAttribute("data-md-color-media"),palette.color.scheme=input.getAttribute("data-md-color-scheme"),palette.color.primary=input.getAttribute("data-md-color-primary"),palette.color.accent=input.getAttribute("data-md-color-accent")}for(var[key,value]of Object.entries(palette.color))document.body.setAttribute("data-md-color-"+key,value)}</script> <label class="md-header__button md-icon" for="__search"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> </label> <div class="md-search" data-md-component="search" role="dialog"> <label class="md-search__overlay" for="__search"></label> <div class="md-search__inner" role="search"> <form class="md-search__form" name="search"> <input type="text" class="md-search__input" name="query" aria-label="Search" placeholder="Search" autocapitalize="off" autocorrect="off" autocomplete="off" spellcheck="false" data-md-component="search-query" required> <label class="md-search__icon md-icon" for="__search"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M9.5 3A6.5 6.5 0 0 1 16 9.5c0 1.61-.59 3.09-1.56 4.23l.27.27h.79l5 5-1.5 1.5-5-5v-.79l-.27-.27A6.52 6.52 0 0 1 9.5 16 6.5 6.5 0 0 1 3 9.5 6.5 6.5 0 0 1 9.5 3m0 2C7 5 5 7 5 9.5S7 14 9.5 14 14 12 14 9.5 12 5 9.5 5"/></svg> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M20 11v2H8l5.5 5.5-1.42 1.42L4.16 12l7.92-7.92L13.5 5.5 8 11z"/></svg> </label> <nav class="md-search__options" aria-label="Search"> <a href="javascript:void(0)" class="md-search__icon md-icon" title="Share" aria-label="Share" data-clipboard data-clipboard-text="" data-md-component="search-share" tabindex="-1"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M18 16.08c-.76 0-1.44.3-1.96.77L8.91 12.7c.05-.23.09-.46.09-.7s-.04-.47-.09-.7l7.05-4.11c.54.5 1.25.81 2.04.81a3 3 0 0 0 3-3 3 3 0 0 0-3-3 3 3 0 0 0-3 3c0 .24.04.47.09.7L8.04 9.81C7.5 9.31 6.79 9 6 9a3 3 0 0 0-3 3 3 3 0 0 0 3 3c.79 0 1.5-.31 2.04-.81l7.12 4.15c-.05.21-.08.43-.08.66 0 1.61 1.31 2.91 2.92 2.91s2.92-1.3 2.92-2.91A2.92 2.92 0 0 0 18 16.08"/></svg> </a> <button type="reset" class="md-search__icon md-icon" title="Clear" aria-label="Clear" tabindex="-1"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M19 6.41 17.59 5 12 10.59 6.41 5 5 6.41 10.59 12 5 17.59 6.41 19 12 13.41 17.59 19 19 17.59 13.41 12z"/></svg> </button> </nav> </form> <div class="md-search__output"> <div class="md-search__scrollwrap" tabindex="0" data-md-scrollfix> <div class="md-search-result" data-md-component="search-result"> <div class="md-search-result__meta"> Initializing search </div> <ol class="md-search-result__list" role="presentation"></ol> </div> </div> </div> </div></div> <div class="md-header__source"> <a href="https://github.com/trapexit/mergerfs" title="Go to repository" class="md-source" data-md-component="source"> <div class="md-source__icon md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512"><!--! Font Awesome Free 6.7.2 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2024 Fonticons, Inc.--><path d="M439.55 236.05 244 40.45a28.87 28.87 0 0 0-40.81 0l-40.66 40.63 51.52 51.52c27.06-9.14 52.68 16.77 43.39 43.68l49.66 49.66c34.23-11.8 61.18 31 35.47 56.69-26.49 26.49-70.21-2.87-56-37.34L240.22 199v121.85c25.3 12.54 22.26 41.85 9.08 55a34.34 34.34 0 0 1-48.55 0c-17.57-17.6-11.07-46.91 11.25-56v-123c-20.8-8.51-24.6-30.74-18.64-45L142.57 101 8.45 235.14a28.86 28.86 0 0 0 0 40.81l195.61 195.6a28.86 28.86 0 0 0 40.8 0l194.69-194.69a28.86 28.86 0 0 0 0-40.81"/></svg> </div> <div class="md-source__repository"> mergerfs </div></a> </div> </nav> </header> <div class="md-container" data-md-component="container"> <main class="md-main" data-md-component="main"> <div class="md-main__inner md-grid"> <div class="md-sidebar md-sidebar--primary" data-md-component="sidebar" data-md-type="navigation" > <div class="md-sidebar__scrollwrap"> <div class="md-sidebar__inner">
<nav class="md-nav md-nav--primary" aria-label="Navigation" data-md-level="0"> <label class="md-nav__title" for="__drawer"> <a href=".." title="mergerfs" class="md-nav__button md-logo" aria-label="mergerfs" data-md-component="logo"> <img src="../logo.jpeg" alt="logo">
</a> mergerfs </label> <div class="md-nav__source"> <a href="https://github.com/trapexit/mergerfs" title="Go to repository" class="md-source" data-md-component="source"> <div class="md-source__icon md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512"><!--! Font Awesome Free 6.7.2 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2024 Fonticons, Inc.--><path d="M439.55 236.05 244 40.45a28.87 28.87 0 0 0-40.81 0l-40.66 40.63 51.52 51.52c27.06-9.14 52.68 16.77 43.39 43.68l49.66 49.66c34.23-11.8 61.18 31 35.47 56.69-26.49 26.49-70.21-2.87-56-37.34L240.22 199v121.85c25.3 12.54 22.26 41.85 9.08 55a34.34 34.34 0 0 1-48.55 0c-17.57-17.6-11.07-46.91 11.25-56v-123c-20.8-8.51-24.6-30.74-18.64-45L142.57 101 8.45 235.14a28.86 28.86 0 0 0 0 40.81l195.61 195.6a28.86 28.86 0 0 0 40.8 0l194.69-194.69a28.86 28.86 0 0 0 0-40.81"/></svg> </div> <div class="md-source__repository"> mergerfs </div></a> </div> <ul class="md-nav__list" data-md-scrollfix> <li class="md-nav__item"> <a href=".." class="md-nav__link"> <span class="md-ellipsis"> Home </span>
</a> </li>
<li class="md-nav__item"> <a href="../quickstart/" class="md-nav__link"> <span class="md-ellipsis"> QuickStart </span>
</a> </li>
<li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type="checkbox" id="__nav_3" > <label class="md-nav__link" for="__nav_3" id="__nav_3_label" tabindex="0"> <span class="md-ellipsis"> Installation </span>
<span class="md-nav__icon md-icon"></span> </label> <nav class="md-nav" data-md-level="1" aria-labelledby="__nav_3_label" aria-expanded="false"> <label class="md-nav__title" for="__nav_3"> <span class="md-nav__icon md-icon"></span> Installation </label> <ul class="md-nav__list" data-md-scrollfix> <li class="md-nav__item"> <a href="../setup/installation/" class="md-nav__link"> <span class="md-ellipsis"> Installation </span>
</a> </li>
<li class="md-nav__item"> <a href="../setup/upgrade/" class="md-nav__link"> <span class="md-ellipsis"> Upgrade </span>
</a> </li>
<li class="md-nav__item"> <a href="../setup/build/" class="md-nav__link"> <span class="md-ellipsis"> Build </span>
</a> </li>
</ul> </nav> </li>
<li class="md-nav__item"> <a href="../terminology/" class="md-nav__link"> <span class="md-ellipsis"> Terminology </span>
</a> </li>
<li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type="checkbox" id="__nav_5" > <label class="md-nav__link" for="__nav_5" id="__nav_5_label" tabindex="0"> <span class="md-ellipsis"> Config </span>
<span class="md-nav__icon md-icon"></span> </label> <nav class="md-nav" data-md-level="1" aria-labelledby="__nav_5_label" aria-expanded="false"> <label class="md-nav__title" for="__nav_5"> <span class="md-nav__icon md-icon"></span> Config </label> <ul class="md-nav__list" data-md-scrollfix> <li class="md-nav__item"> <a href="../config/options/" class="md-nav__link"> <span class="md-ellipsis"> Options </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/deprecated_options/" class="md-nav__link"> <span class="md-ellipsis"> Deprecated Options </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/branches/" class="md-nav__link"> <span class="md-ellipsis"> branches </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/functions_categories_and_policies/" class="md-nav__link"> <span class="md-ellipsis"> functions, categories and policies </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/func_readdir/" class="md-nav__link"> <span class="md-ellipsis"> func.readdir </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/rename_and_link/" class="md-nav__link"> <span class="md-ellipsis"> rename and link </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/cache/" class="md-nav__link"> <span class="md-ellipsis"> caching </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/readahead/" class="md-nav__link"> <span class="md-ellipsis"> readahead </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/inodecalc/" class="md-nav__link"> <span class="md-ellipsis"> inodecalc </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/threads/" class="md-nav__link"> <span class="md-ellipsis"> threads </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/pin-threads/" class="md-nav__link"> <span class="md-ellipsis"> pin-threads </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/link_cow/" class="md-nav__link"> <span class="md-ellipsis"> link_cow </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/fuse_msg_size/" class="md-nav__link"> <span class="md-ellipsis"> fuse_msg_size </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/follow-symlinks/" class="md-nav__link"> <span class="md-ellipsis"> follow-symlinks </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/link-exdev/" class="md-nav__link"> <span class="md-ellipsis"> link-exdev </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/rename-exdev/" class="md-nav__link"> <span class="md-ellipsis"> rename-exdev </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/symlinkify/" class="md-nav__link"> <span class="md-ellipsis"> symlinkify </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/nullrw/" class="md-nav__link"> <span class="md-ellipsis"> nullrw </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/xattr/" class="md-nav__link"> <span class="md-ellipsis"> xattr </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/nfsopenhack/" class="md-nav__link"> <span class="md-ellipsis"> nfsopenhack </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/statfs/" class="md-nav__link"> <span class="md-ellipsis"> statfs / statvfs </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/flush-on-close/" class="md-nav__link"> <span class="md-ellipsis"> flush-on-close </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/export-support/" class="md-nav__link"> <span class="md-ellipsis"> export-support </span>
</a> </li>
</ul> </nav> </li>
<li class="md-nav__item"> <a href="../error_handling_and_logging/" class="md-nav__link"> <span class="md-ellipsis"> Error Handling and Logging </span>
</a> </li>
<li class="md-nav__item"> <a href="../runtime_interfaces/" class="md-nav__link"> <span class="md-ellipsis"> Runtime Interfaces </span>
</a> </li>
<li class="md-nav__item"> <a href="../remote_filesystems/" class="md-nav__link"> <span class="md-ellipsis"> Remote Filesystems </span>
</a> </li>
<li class="md-nav__item"> <a href="../tips_notes/" class="md-nav__link"> <span class="md-ellipsis"> Tips and Notes </span>
</a> </li>
<li class="md-nav__item"> <a href="../known_issues_bugs/" class="md-nav__link"> <span class="md-ellipsis"> Known Issues and Bugs </span>
</a> </li>
<li class="md-nav__item"> <a href="../project_comparisons/" class="md-nav__link"> <span class="md-ellipsis"> Project Comparisons </span>
</a> </li>
<li class="md-nav__item"> <a href="../performance/" class="md-nav__link"> <span class="md-ellipsis"> Tweaking Performance </span>
</a> </li>
<li class="md-nav__item"> <a href="../benchmarking/" class="md-nav__link"> <span class="md-ellipsis"> Benchmarking </span>
</a> </li>
<li class="md-nav__item"> <a href="../tooling/" class="md-nav__link"> <span class="md-ellipsis"> Tooling </span>
</a> </li>
<li class="md-nav__item md-nav__item--active"> <input class="md-nav__toggle md-toggle" type="checkbox" id="__toc"> <label class="md-nav__link md-nav__link--active" for="__toc"> <span class="md-ellipsis"> Usage Patterns </span>
<span class="md-nav__icon md-icon"></span> </label> <a href="./" class="md-nav__link md-nav__link--active"> <span class="md-ellipsis"> Usage Patterns </span>
</a>
<nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class="md-nav__title" for="__toc"> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class="md-nav__list" data-md-component="toc" data-md-scrollfix> <li class="md-nav__item"> <a href="#tiered-cache" class="md-nav__link"> <span class="md-ellipsis"> tiered cache </span> </a> <nav class="md-nav" aria-label="tiered cache"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#time-based-expiring" class="md-nav__link"> <span class="md-ellipsis"> time based expiring </span> </a> </li> <li class="md-nav__item"> <a href="#percentage-full-expiring" class="md-nav__link"> <span class="md-ellipsis"> percentage full expiring </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li>
<li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type="checkbox" id="__nav_16" > <label class="md-nav__link" for="__nav_16" id="__nav_16_label" tabindex="0"> <span class="md-ellipsis"> FAQ </span>
<span class="md-nav__icon md-icon"></span> </label> <nav class="md-nav" data-md-level="1" aria-labelledby="__nav_16_label" aria-expanded="false"> <label class="md-nav__title" for="__nav_16"> <span class="md-nav__icon md-icon"></span> FAQ </label> <ul class="md-nav__list" data-md-scrollfix> <li class="md-nav__item"> <a href="../faq/reliability_and_scalability/" class="md-nav__link"> <span class="md-ellipsis"> Reliability and Scalability </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/usage_and_functionality/" class="md-nav__link"> <span class="md-ellipsis"> Usage and Functionality </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/configuration_and_policies/" class="md-nav__link"> <span class="md-ellipsis"> Configuration and Policies </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/compatibility_and_integration/" class="md-nav__link"> <span class="md-ellipsis"> Compatibility and Integration </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/recommendations_and_warnings/" class="md-nav__link"> <span class="md-ellipsis"> Recommendations and Warnings </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/technical_behavior_and_limitations/" class="md-nav__link"> <span class="md-ellipsis"> Technical Behavior and Limitations </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/limit_drive_spinup/" class="md-nav__link"> <span class="md-ellipsis"> Limiting drive spinup </span>
</a> </li>
</ul> </nav> </li>
<li class="md-nav__item"> <a href="../related_projects/" class="md-nav__link"> <span class="md-ellipsis"> Related Projects </span>
</a> </li>
<li class="md-nav__item"> <a href="../media_and_publicity/" class="md-nav__link"> <span class="md-ellipsis"> Media and Publicity </span>
</a> </li>
<li class="md-nav__item"> <a href="../support/" class="md-nav__link"> <span class="md-ellipsis"> Support </span>
</a> </li>
<li class="md-nav__item"> <a href="../sponsorship_and_donations/" class="md-nav__link"> <span class="md-ellipsis"> Sponsorship and Donations </span>
</a> </li>
</ul></nav> </div> </div> </div> <div class="md-sidebar md-sidebar--secondary" data-md-component="sidebar" data-md-type="toc" > <div class="md-sidebar__scrollwrap"> <div class="md-sidebar__inner">
<nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class="md-nav__title" for="__toc"> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class="md-nav__list" data-md-component="toc" data-md-scrollfix> <li class="md-nav__item"> <a href="#tiered-cache" class="md-nav__link"> <span class="md-ellipsis"> tiered cache </span> </a> <nav class="md-nav" aria-label="tiered cache"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#time-based-expiring" class="md-nav__link"> <span class="md-ellipsis"> time based expiring </span> </a> </li> <li class="md-nav__item"> <a href="#percentage-full-expiring" class="md-nav__link"> <span class="md-ellipsis"> percentage full expiring </span> </a> </li> </ul> </nav> </li> </ul> </nav> </div> </div> </div> <div class="md-content" data-md-component="content"> <article class="md-content__inner md-typeset">
<a href="https://github.com/trapexit/mergerfs/edit/master/mkdocs/docs/usage_patterns.md" title="Edit this page" class="md-content__button md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M10 20H6V4h7v5h5v3.1l2-2V8l-6-6H6c-1.1 0-2 .9-2 2v16c0 1.1.9 2 2 2h4zm10.2-7c.1 0 .3.1.4.2l1.3 1.3c.2.2.2.6 0 .8l-1 1-2.1-2.1 1-1c.1-.1.2-.2.4-.2m0 3.9L14.1 23H12v-2.1l6.1-6.1z"/></svg> </a> <a href="https://github.com/trapexit/mergerfs/raw/master/mkdocs/docs/usage_patterns.md" title="View source of this page" class="md-content__button md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M17 18c.56 0 1 .44 1 1s-.44 1-1 1-1-.44-1-1 .44-1 1-1m0-3c-2.73 0-5.06 1.66-6 4 .94 2.34 3.27 4 6 4s5.06-1.66 6-4c-.94-2.34-3.27-4-6-4m0 6.5a2.5 2.5 0 0 1-2.5-2.5 2.5 2.5 0 0 1 2.5-2.5 2.5 2.5 0 0 1 2.5 2.5 2.5 2.5 0 0 1-2.5 2.5M9.27 20H6V4h7v5h5v4.07c.7.08 1.36.25 2 .49V8l-6-6H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h4.5a8.2 8.2 0 0 1-1.23-2"/></svg> </a>
<h1 id="usage-patterns">Usage Patterns</h1><h2 id="tiered-cache">tiered cache</h2><p>Some storage technologies support what is called "tiered" caching. Theplacing of smaller, faster storage as a transparent cache to larger,slower storage. NVMe, SSD, Optane in front of traditional HDDs forinstance.</p><p>mergerfs does not natively support any sort of tiered caching. Mostusers have no use for such a feature and its inclusion wouldcomplicate the code as it exists today. However, there are a fewsituations where a cache filesystem could help with a typical mergerfssetup.</p><ol><li>Fast network, slow filesystems, many readers: You've a 10+Gbps network with many readers and your regular filesystems can't keep up.</li><li>Fast network, slow filesystems, small'ish bursty writes: You have a 10+Gbps network and wish to transfer amounts of data less than your cache filesystem but wish to do so quickly and the time between bursts is long enough to migrate data.</li></ol><p>With #1 it's arguable if you should be using mergerfs at all. A RAIDlevel that can aggregate performance or using higher performancestorage would probably be the better solution. If you're going to usemergerfs there are other tactics that may help: spreading the dataacross filesystems (see the mergerfs.dup tool) and setting<code>func.open=rand</code>, using <code>symlinkify</code>, or using dm-cache or a similartechnology to add tiered cache to the underlying device itself.</p><p>With #2 one could use a block cache solution as available via LVM anddm-cache but there is another solution which requires only mergerfs, ascript to move files around, and a cron job to run said script.</p><ul><li>Create two mergerfs pools. One which includes just the <strong>slow</strong> branches and one which has both the <strong>fast</strong> branches (SSD,NVME,etc.) and <strong>slow</strong> branches. The <strong>base</strong> pool and the <strong>cache</strong> pool.</li><li>The <strong>cache</strong> pool should have the cache branches listed first in the branch list in order to to make it easier to prioritize them.</li><li>The best <code>create</code> policies to use for the <strong>cache</strong> pool would probably be <code>ff</code>, <code>lus</code>, or <code>lfs</code>. The latter two under the assumption that the cache filesystem(s) are far smaller than the backing filesystems.</li><li>You can also set the <strong>slow</strong> filesystems mode to <code>NC</code> which would give you the ability to use other <code>create</code> policies though that'd mean if the cache filesystems fill you'd get "out of space" errors. This however may be good as it would indicate the script moving files around is not configured properly.</li><li>Set your programs to use the <strong>cache</strong> pool.</li><li>Configure the <strong>base</strong> pool with the <code>create</code> policy you would like to lay out files as you like.</li><li>Save one of the below scripts or create your own. The script's responsibility is to move files from the <strong>cache</strong> branches (not pool) to the <strong>base</strong> pool.</li><li>Use <code>cron</code> (as root) to schedule the command at whatever frequency is appropriate for your workflow.</li></ul><h3 id="time-based-expiring">time based expiring</h3><p>Move files from cache filesystem to base pool which have an accesstime older than the supplied number of days. Replace <code>-atime</code> with<code>-amin</code> in the script if you want minutes rather than days.</p><p><strong>NOTE:</strong> The arguments to these scripts include the cache<strong>filesystem</strong> itself. Not the pool with the cache filesystem. Youcould have data loss if the source is the cache pool.</p><p><a href="https://github.com/trapexit/mergerfs/blob/latest-release/tools/mergerfs.time-based-mover?raw=1">mergerfs.time-based-mover</a></p><p>Download:<div class="language-text highlight"><pre><span></span><code><span id="__span-0-1"><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a>curl -o /usr/local/bin/mergerfs.time-based-mover https://raw.githubusercontent.com/trapexit/mergerfs/refs/heads/latest-release/tools/mergerfs.time-based-mover</span></code></pre></div></p><p>crontab entry:<div class="language-text highlight"><pre><span></span><code><span id="__span-1-1"><a id="__codelineno-1-1" name="__codelineno-1-1" href="#__codelineno-1-1"></a># m h dom mon dow command</span><span id="__span-1-2"><a id="__codelineno-1-2" name="__codelineno-1-2" href="#__codelineno-1-2"></a>0 * * * * /usr/local/bin/mergerfs.time-based-mover /mnt/ssd/cache00 /mnt/base-pool 1</span></code></pre></div></p><p>If you have more than one cache filesystem then simply add a cronentry for each.</p><p>If you want to only move files from a subdirectory then use thesubdirectories. <code>/mnt/ssd/cache00/foo</code> and <code>/mnt/base-pool/foo</code>respectively.</p><h3 id="percentage-full-expiring">percentage full expiring</h3><p>While the cache filesystem's percentage full is above the providedvalue move the oldest file from the cache filesystem to the base pool.</p><p><strong>NOTE:</strong> The arguments to these scripts include the cache<strong>filesystem</strong> itself. Not the pool with the cache filesystem. Youcould have data loss if the source is the cache pool.</p><p><a href="https://github.com/trapexit/mergerfs/blob/latest-release/tools/mergerfs.percent-full-mover?raw=1">mergerfs.percent-full-mover</a></p><p>Download:<div class="language-text highlight"><pre><span></span><code><span id="__span-2-1"><a id="__codelineno-2-1" name="__codelineno-2-1" href="#__codelineno-2-1"></a>curl -o /usr/local/bin/mergerfs.percent-full-mover https://raw.githubusercontent.com/trapexit/mergerfs/refs/heads/latest-release/tools/mergerfs.percent-full-mover</span></code></pre></div></p><p>crontab entry:<div class="language-text highlight"><pre><span></span><code><span id="__span-3-1"><a id="__codelineno-3-1" name="__codelineno-3-1" href="#__codelineno-3-1"></a># m h dom mon dow command</span><span id="__span-3-2"><a id="__codelineno-3-2" name="__codelineno-3-2" href="#__codelineno-3-2"></a>0 * * * * /usr/local/bin/mergerfs.percent-full-mover /mnt/ssd/cache00 /mnt/base-pool 80</span></code></pre></div></p><p>If you have more than one cache filesystem then simply add a cronentry for each.</p><p>If you want to only move files from a subdirectory then use thesubdirectories. <code>/mnt/ssd/cache00/foo</code> and <code>/mnt/base-pool/foo</code>respectively.</p>
</article> </div> <script>var target=document.getElementById(location.hash.slice(1));target&&target.name&&(target.checked=target.name.startsWith("__tabbed_"))</script> </div> <button type="button" class="md-top md-icon" data-md-component="top" hidden> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8z"/></svg> Back to top</button> </main> <footer class="md-footer"> <nav class="md-footer__inner md-grid" aria-label="Footer" > <a href="../tooling/" class="md-footer__link md-footer__link--prev" aria-label="Previous: Tooling"> <div class="md-footer__button md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M20 11v2H8l5.5 5.5-1.42 1.42L4.16 12l7.92-7.92L13.5 5.5 8 11z"/></svg> </div> <div class="md-footer__title"> <span class="md-footer__direction"> Previous </span> <div class="md-ellipsis"> Tooling </div> </div> </a> <a href="../faq/reliability_and_scalability/" class="md-footer__link md-footer__link--next" aria-label="Next: Reliability and Scalability"> <div class="md-footer__title"> <span class="md-footer__direction"> Next </span> <div class="md-ellipsis"> Reliability and Scalability </div> </div> <div class="md-footer__button md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M4 11v2h12l-5.5 5.5 1.42 1.42L19.84 12l-7.92-7.92L10.5 5.5 16 11z"/></svg> </div> </a> </nav> <div class="md-footer-meta md-typeset"> <div class="md-footer-meta__inner md-grid"> <div class="md-copyright"> Made with <a href="https://squidfunk.github.io/mkdocs-material/" target="_blank" rel="noopener"> Material for MkDocs </a> </div> </div> </div></footer> </div> <div class="md-dialog" data-md-component="dialog"> <div class="md-dialog__inner md-typeset"></div> </div> <script id="__config" type="application/json">{"base": "..", "features": ["content.action.edit", "content.action.view", "content.code.copy", "content.code.select", "navigation.footer", "navigation.instant", "navigation.instant.prefetch", "navigation.path", "navigation.top", "navigation.tracking", "optimize", "search.share", "toc.follow"], "search": "../assets/javascripts/workers/search.f8cc74c7.min.js", "translations": {"clipboard.copied": "Copied to clipboard", "clipboard.copy": "Copy to clipboard", "search.result.more.one": "1 more on this page", "search.result.more.other": "# more on this page", "search.result.none": "No matching documents", "search.result.one": "1 matching document", "search.result.other": "# matching documents", "search.result.placeholder": "Type to start searching", "search.result.term.missing": "Missing", "select.version": "Select version"}}</script> <script src="../assets/javascripts/bundle.60a45f97.min.js"></script> </body></html>
|
