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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-policies-should-i-use" class="md-nav__link"> <span class="md-ellipsis"> What policies should I use? </span> </a> </li> <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="#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-policies-should-i-use">What policies should I use?</h2><p>Unless you're doing something more niche the average user is probablybest off using <code>mfs</code> for <code>category.create</code>. It will spread files outacross your branches based on available space. Use <code>mspmfs</code> if youwant to try to colocate the data a bit more. You may want to use <code>lus</code>if you prefer a slightly different distribution of data if you have amix of smaller and larger filesystems. Generally though <code>mfs</code>, <code>lus</code>,or even <code>rand</code> are good for the general use case. If you are startingwith an imbalanced pool you can use the tool <strong>mergerfs.balance</strong> toredistribute files across the pool. That said "balancing" reallyshould not be needed. There is really no inherent issue with beingunbalanced. "Optimal" layout is related to usage patterns and mostpeople don't have patterns that are performance sensitive or specificenough to do anything about. Additionally, the balance tool is verysimplistic and was not written to be as serious tool that accounts foredge cases.</p><p>If you really wish to try to colocate files based on directory you canset <code>func.create</code> to <code>epmfs</code> or similar and <code>func.mkdir</code> to <code>rand</code> or<code>eprand</code> depending on if you just want to colocate generally or onspecific branches. Either way the <em>need</em> to colocate is rare. Forinstance: if you wish to remove the device regularly and want the datato predictably be on that device or if you don't use backup at all anddon't wish to replace that data piecemeal. In which case using pathpreservation can help but will require some manualattention. Colocating after the fact can be accomplished using the<strong>mergerfs.consolidate</strong> tool. If you don't need strict colocationwhich the <code>ep</code> policies provide then you can use the <code>msp</code> basedpolicies which will walk back the path till finding a branch thatworks.</p><p>Ultimately there is no correct answer. It is a preference or based onsome particular need. mergerfs is very easy to test and experimentwith. I suggest creating a test setup and experimenting to get a senseof what you want.</p><p><code>epmfs</code> is the default <code>category.create</code> policy because <code>ep</code> policiesare not going to change the general layout of the branches. It won'tplace files/dirs on branches that don't already have the relativebranch. So it keeps the system in a known state. It's much easier tostop using <code>epmfs</code> or redistribute files around the filesystem than itis to consolidate them back.</p><h2 id="what-settings-should-i-use">What settings should I use?</h2><p>Depends on what features you want. Generally speaking, there are no"wrong" settings. All settings are feature related. The best bet is toread over the available options and choose what fits yoursituation. If something isn't clear from the documentation pleasereach out and the documentation will be improved.</p><p>For the average person the settings described in the <a href="../../quickstart/">QuickStart</a> are sufficient.</p><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 thatfirst directory will be placed on the same branch because it ispreserving paths.</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>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 beforetransferring your data.</p>
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