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89 lines
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89 lines
3.4 KiB
ReStructuredText
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CephFS best practices
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=====================
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This guide provides recommendations for best results when deploying CephFS.
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For the actual configuration guide for CephFS, please see the instructions
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at :doc:`/cephfs/index`.
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Which Ceph version?
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-------------------
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Use at least the Jewel (v10.2.0) release of Ceph. This is the first
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release to include stable CephFS code and fsck/repair tools. Make sure
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you are using the latest point release to get bug fixes.
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Note that Ceph releases do not include a kernel, this is versioned
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and released separately. See below for guidance of choosing an
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appropriate kernel version if you are using the kernel client
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for CephFS.
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Most stable configuration
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-------------------------
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Some features in CephFS are still experimental. See
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:doc:`/cephfs/experimental-features` for guidance on these.
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For the best chance of a happy healthy filesystem, use a **single active MDS**
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and **do not use snapshots**. Both of these are the default.
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Note that creating multiple MDS daemons is fine, as these will simply be
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used as standbys. However, for best stability you should avoid
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adjusting ``max_mds`` upwards, as this would cause multiple MDS
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daemons to be active at once.
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Which client?
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-------------
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The FUSE client is the most accessible and the easiest to upgrade to the
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version of Ceph used by the storage cluster, while the kernel client will
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often give better performance.
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The clients do not always provide equivalent functionality, for example
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the fuse client supports client-enforced quotas while the kernel client
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does not.
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When encountering bugs or performance issues, it is often instructive to
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try using the other client, in order to find out whether the bug was
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client-specific or not (and then to let the developers know).
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Which kernel version?
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---------------------
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Because the kernel client is distributed as part of the linux kernel (not
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as part of packaged ceph releases),
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you will need to consider which kernel version to use on your client nodes.
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Older kernels are known to include buggy ceph clients, and may not support
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features that more recent Ceph clusters support.
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Remember that the "latest" kernel in a stable linux distribution is likely
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to be years behind the latest upstream linux kernel where Ceph development
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takes place (including bug fixes).
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As a rough guide, as of Ceph 10.x (Jewel), you should be using a least a
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4.x kernel. If you absolutely have to use an older kernel, you should use
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the fuse client instead of the kernel client.
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This advice does not apply if you are using a linux distribution that
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includes CephFS support, as in this case the distributor will be responsible
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for backporting fixes to their stable kernel: check with your vendor.
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Reporting issues
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----------------
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If you have identified a specific issue, please report it with as much
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information as possible. Especially important information:
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* Ceph versions installed on client and server
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* Whether you are using the kernel or fuse client
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* If you are using the kernel client, what kernel version?
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* How many clients are in play, doing what kind of workload?
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* If a system is 'stuck', is that affecting all clients or just one?
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* Any ceph health messages
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* Any backtraces in the ceph logs from crashes
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If you are satisfied that you have found a bug, please file it on
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`the tracker <http://tracker.ceph.com>`_. For more general queries please write
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to the `ceph-users mailing list <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com/>`_.
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