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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="#can-mergerfs-be-used-with-filesystems-which-already-have-data-are-in-use" class="md-nav__link"> <span class="md-ellipsis"> Can mergerfs be used with filesystems which already have data / are in use? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-removed-from-the-pool-without-affecting-them" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be removed from the pool without affecting them? </span> </a> </li> <li class="md-nav__item"> <a href="#can-mergerfs-be-removed-without-affecting-the-data" class="md-nav__link"> <span class="md-ellipsis"> Can mergerfs be removed without affecting the data? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-moved-to-another-pool" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be moved to another pool? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-part-of-multiple-pools" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be part of multiple pools? </span> </a> </li> <li class="md-nav__item"> <a href="#how-do-i-migrate-data-into-or-out-of-the-pool-when-addingremoving-filesystems" class="md-nav__link"> <span class="md-ellipsis"> How do I migrate data into or out of the pool when adding/removing filesystems? </span> </a> </li> <li class="md-nav__item"> <a href="#how-do-i-remove-a-filesystem-but-keep-the-data-in-the-pool" class="md-nav__link"> <span class="md-ellipsis"> How do I remove a filesystem but keep the data in the pool? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-written-to-directly-outside-of-mergerfs-while-pooled" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be written to directly? Outside of mergerfs while pooled? </span> </a> </li> </ul> </nav> </li>
<li class="md-nav__item"> <a href="../configuration_and_policies/" class="md-nav__link"> <span class="md-ellipsis"> Configuration and Policies </span>
</a> </li>
<li class="md-nav__item"> <a href="../compatibility_and_integration/" class="md-nav__link"> <span class="md-ellipsis"> Compatibility and Integration </span>
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<li class="md-nav__item"> <a href="../recommendations_and_warnings/" class="md-nav__link"> <span class="md-ellipsis"> Recommendations and Warnings </span>
</a> </li>
<li class="md-nav__item"> <a href="../technical_behavior_and_limitations/" class="md-nav__link"> <span class="md-ellipsis"> Technical Behavior and Limitations </span>
</a> </li>
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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="#can-mergerfs-be-used-with-filesystems-which-already-have-data-are-in-use" class="md-nav__link"> <span class="md-ellipsis"> Can mergerfs be used with filesystems which already have data / are in use? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-removed-from-the-pool-without-affecting-them" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be removed from the pool without affecting them? </span> </a> </li> <li class="md-nav__item"> <a href="#can-mergerfs-be-removed-without-affecting-the-data" class="md-nav__link"> <span class="md-ellipsis"> Can mergerfs be removed without affecting the data? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-moved-to-another-pool" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be moved to another pool? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-part-of-multiple-pools" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be part of multiple pools? </span> </a> </li> <li class="md-nav__item"> <a href="#how-do-i-migrate-data-into-or-out-of-the-pool-when-addingremoving-filesystems" class="md-nav__link"> <span class="md-ellipsis"> How do I migrate data into or out of the pool when adding/removing filesystems? </span> </a> </li> <li class="md-nav__item"> <a href="#how-do-i-remove-a-filesystem-but-keep-the-data-in-the-pool" class="md-nav__link"> <span class="md-ellipsis"> How do I remove a filesystem but keep the data in the pool? </span> </a> </li> <li class="md-nav__item"> <a href="#can-filesystems-be-written-to-directly-outside-of-mergerfs-while-pooled" class="md-nav__link"> <span class="md-ellipsis"> Can filesystems be written to directly? Outside of mergerfs while pooled? </span> </a> </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/tree/master/mkdocs/docs/faq/usage_and_functionality.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/tree/master/mkdocs/docs/faq/usage_and_functionality.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-and-functionality">Usage and Functionality</h1><h2 id="can-mergerfs-be-used-with-filesystems-which-already-have-data-are-in-use">Can mergerfs be used with filesystems which already have data / are in use?</h2><p>Yes. mergerfs is really just a proxy and does <strong>NOT</strong> interfere withthe normal form or function of the filesystems, mounts, paths itmanages. A userland application that is acting as aman-in-the-middle. It can't do anything that any other random piece ofsoftware can't do.</p><p>mergerfs is <strong>not</strong> a traditional filesystem that takes control overthe underlying block device. mergerfs is <strong>not</strong> RAID. It does <strong>not</strong>manipulate the data that passes through it. It does <strong>not</strong> shard dataacross filesystems. It merely shards some <strong>behavior</strong> and aggregatesothers.</p><h2 id="can-filesystems-be-removed-from-the-pool-without-affecting-them">Can filesystems be removed from the pool without affecting them?</h2><p>Yes. See previous question's answer.</p><h2 id="can-mergerfs-be-removed-without-affecting-the-data">Can mergerfs be removed without affecting the data?</h2><p>Yes. See the previous question's answer.</p><h2 id="can-filesystems-be-moved-to-another-pool">Can filesystems be moved to another pool?</h2><p>Yes. See the previous question's answer.</p><h2 id="can-filesystems-be-part-of-multiple-pools">Can filesystems be part of multiple pools?</h2><p>Yes.</p><h2 id="how-do-i-migrate-data-into-or-out-of-the-pool-when-addingremoving-filesystems">How do I migrate data into or out of the pool when adding/removing filesystems?</h2><p>You don't need to. See the previous question's answer.</p><h2 id="how-do-i-remove-a-filesystem-but-keep-the-data-in-the-pool">How do I remove a filesystem but keep the data in the pool?</h2><p>Nothing special needs to be done. Remove the branch from mergerfs'config and copy (rsync) the data from the removed filesystem into thepool. The same as if it were you transfering data from one filesystemto another.</p><p>If you wish to continue using the pool while performing the transfersimply create a temporary pool without the filesystem in question andthen copy the data. It would probably be a good idea to set the branchto <code>RO</code> prior to doing this to ensure no new content is written to thefilesystem while performing the copy.</p><h2 id="can-filesystems-be-written-to-directly-outside-of-mergerfs-while-pooled">Can filesystems be written to directly? Outside of mergerfs while pooled?</h2><p>Yes, however, it's not recommended to use the same file from within thepool and from without at the same time (particularlywriting). Especially if using caching of any kind (cache.files,cache.entry, cache.attr, cache.negative_entry, cache.symlinks,cache.readdir, etc.) as there could be a conflict between cached dataand not.</p>
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