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<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="#what-settings-should-i-use" class="md-nav__link"> <span class="md-ellipsis"> What settings should I use? </span> </a> </li> <li class="md-nav__item"> <a href="#how-can-i-ensure-files-are-collocated-on-the-same-branch" class="md-nav__link"> <span class="md-ellipsis"> How can I ensure files are collocated on the same branch? </span> </a> </li> <li class="md-nav__item"> <a href="#how-can-i-balance-files-across-the-pool" class="md-nav__link"> <span class="md-ellipsis"> How can I balance files across the pool? </span> </a> </li> <li class="md-nav__item"> <a href="#why-are-all-my-files-ending-up-on-1-filesystem" class="md-nav__link"> <span class="md-ellipsis"> Why are all my files ending up on 1 filesystem?! </span> </a> </li> </ul> </nav> </div> </div> </div> <div class="md-content" data-md-component="content"> <article class="md-content__inner md-typeset">
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<h1 id="configuration-and-policies">Configuration and Policies</h1><h2 id="what-settings-should-i-use">What settings should I use?</h2><p>Depends on what features you want. Generally, there are no "good","bad", "inefficient", or "optimal" settings. Options are almostexclusively functional. Meaning they change the behavior of thesoftware. It is best to read over the available options and choosewhat fits your use case. If something is not clear from thedocumentation please reach out and the documentation will be improved.</p><p>The settings described in the <a href="../../quickstart/">Quick Start</a> aresufficient for most users.</p><p>Filesystems are complex and use cases numerous. There simply is no wayto provide a singular setup that works for all situations. Sincemergerfs <a href="../usage_and_functionality/">does not impact</a> the underlyingfilesystems and can be added or removed without any impact it isextremely easy to test and experiment with different settings.</p><h2 id="how-can-i-ensure-files-are-collocated-on-the-same-branch">How can I ensure files are collocated on the same branch?</h2><p>Many people like the idea of ensuring related files, such as all thefiles to a TV show season or songs in an album, are stored on the samestorage device. However, most people have no actual need for thisbehavior.</p><ol><li>If you backup your data it is extremely likely your backup solution can restore only those files you are missing.</li><li>Software such as <strong>Sonarr</strong> can manage the downloading and post processing of bespoke episodes which may be missing in a season. Either by downloading the episode individually if available or by downloading a full season.</li><li>There is no benefit to keeping files collocated with regard to drive spinup, caching, or other secondary concern.</li></ol><p>The main use case for wanting collocation is where the branch is goingto be removed from the pool and you wish to have all data from somelogical set on that device. Such as you intend to take a drive out ofthe pool to take on a trip and want a whole show on thedrive. However, even in these situations you typically end up needingto curate the files anyway because it has show A but not show B.</p><p>All that said you can accomplish collocation to varying degrees usingthe following methods:</p><ol><li>Use <a href="https://github.com/trapexit/mergerfs-tools/blob/master/src/mergerfs.consolidate">mergerfs.consolidate</a> when consolidation is needed.</li><li>Use a <code>msp</code> create policy.</li><li>Use <code>epmfs</code> or other <code>ep</code> create policy and manually create paths on the branches directly.</li><li>Use a <code>ep</code> <code>create</code> policy and <code>rand</code> for <code>mkdir</code>.</li></ol><h2 id="how-can-i-balance-files-across-the-pool">How can I balance files across the pool?</h2><p>Similar to collocation there is generally little reason to balancefiles.</p><ol><li>Since prediction of a filesystem's death or loss of data is near impossible there is little reason to balance in hopes of limiting data loss.</li><li>While performance could be impacted by having too much reading or writing happen to singular underlying filesystems balancing won't help unless you have the ability to manage the access patterns to the pool.</li><li>Over time most configurations will lead to a random distribution of files across the branches which is effectively "balancing."</li></ol><p>If you wish to move files around or balance the pool you can:</p><ol><li>Use <code>rand</code> or <code>pfrd</code> create policies and just use your system as normal.</li><li>Write simple scripts using rsync or similar to move files around as you wish.</li><li>Use <a href="https://github.com/trapexit/mergerfs-tools/blob/master/src/mergerfs.balance">mergerfs.balance</a>. Keep in mind that this tool is really just an example of how to accomplish such a task.</li></ol><h2 id="why-are-all-my-files-ending-up-on-1-filesystem">Why are all my files ending up on 1 filesystem?!</h2><p>Did you start with empty filesystems? Did you explicitly configure a<code>category.create</code> policy? Are you using an <code>existing path</code> / <code>pathpreserving</code> policy?</p><p>The default create policy is <code>epmfs</code>. That is a path preservingalgorithm. With such a policy for <code>mkdir</code> and <code>create</code> with a set ofempty filesystems it will select only 1 filesystem when the firstdirectory is created. Anything, files or directories, created in thatdirectory will be placed on the same branch because it is preservingpaths.</p><p>This may catch new users off guard but this policy is the safestpolicy to start with as it will not change the general layout of theunderlying filesystems. If you do not care about path preservation(most shouldn't) and wish your files to be spread across all yourfilesystems change to <code>rand</code>, <code>pfrd</code>, <code>mfs</code> or similar<a href="../../config/functions_categories_and_policies/">policy</a>. If you dowant path preservation you'll need to perform the manual act ofcreating paths on the filesystems you want the data to land on beforewriting said data.</p>
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