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1 | |
2 | CephFS best practices | |
3 | ===================== | |
4 | ||
5 | This guide provides recommendations for best results when deploying CephFS. | |
6 | ||
7 | For the actual configuration guide for CephFS, please see the instructions | |
8 | at :doc:`/cephfs/index`. | |
9 | ||
10 | Which Ceph version? | |
11 | ------------------- | |
12 | ||
13 | Use at least the Jewel (v10.2.0) release of Ceph. This is the first | |
14 | release to include stable CephFS code and fsck/repair tools. Make sure | |
15 | you are using the latest point release to get bug fixes. | |
16 | ||
17 | Note that Ceph releases do not include a kernel, this is versioned | |
18 | and released separately. See below for guidance of choosing an | |
19 | appropriate kernel version if you are using the kernel client | |
20 | for CephFS. | |
21 | ||
22 | Most stable configuration | |
23 | ------------------------- | |
24 | ||
25 | Some features in CephFS are still experimental. See | |
26 | :doc:`/cephfs/experimental-features` for guidance on these. | |
27 | ||
28 | For the best chance of a happy healthy filesystem, use a **single active MDS** | |
29 | and **do not use snapshots**. Both of these are the default. | |
30 | ||
31 | Note that creating multiple MDS daemons is fine, as these will simply be | |
32 | used as standbys. However, for best stability you should avoid | |
b32b8144 | 33 | adjusting ``max_mds`` upwards, as this would cause multiple MDS |
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34 | daemons to be active at once. |
35 | ||
36 | Which client? | |
37 | ------------- | |
38 | ||
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39 | The FUSE client is the most accessible and the easiest to upgrade to the |
40 | version of Ceph used by the storage cluster, while the kernel client will | |
41 | often give better performance. | |
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42 | |
43 | The clients do not always provide equivalent functionality, for example | |
44 | the fuse client supports client-enforced quotas while the kernel client | |
45 | does not. | |
46 | ||
47 | When encountering bugs or performance issues, it is often instructive to | |
48 | try using the other client, in order to find out whether the bug was | |
49 | client-specific or not (and then to let the developers know). | |
50 | ||
51 | Which kernel version? | |
b32b8144 | 52 | --------------------- |
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53 | |
54 | Because the kernel client is distributed as part of the linux kernel (not | |
55 | as part of packaged ceph releases), | |
56 | you will need to consider which kernel version to use on your client nodes. | |
57 | Older kernels are known to include buggy ceph clients, and may not support | |
58 | features that more recent Ceph clusters support. | |
59 | ||
60 | Remember that the "latest" kernel in a stable linux distribution is likely | |
61 | to be years behind the latest upstream linux kernel where Ceph development | |
62 | takes place (including bug fixes). | |
63 | ||
64 | As a rough guide, as of Ceph 10.x (Jewel), you should be using a least a | |
65 | 4.x kernel. If you absolutely have to use an older kernel, you should use | |
66 | the fuse client instead of the kernel client. | |
67 | ||
68 | This advice does not apply if you are using a linux distribution that | |
69 | includes CephFS support, as in this case the distributor will be responsible | |
70 | for backporting fixes to their stable kernel: check with your vendor. | |
71 | ||
72 | Reporting issues | |
73 | ---------------- | |
74 | ||
75 | If you have identified a specific issue, please report it with as much | |
76 | information as possible. Especially important information: | |
77 | ||
78 | * Ceph versions installed on client and server | |
79 | * Whether you are using the kernel or fuse client | |
80 | * If you are using the kernel client, what kernel version? | |
81 | * How many clients are in play, doing what kind of workload? | |
82 | * If a system is 'stuck', is that affecting all clients or just one? | |
83 | * Any ceph health messages | |
84 | * Any backtraces in the ceph logs from crashes | |
85 | ||
86 | If you are satisfied that you have found a bug, please file it on | |
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87 | `the tracker <http://tracker.ceph.com>`_. For more general queries please write |
88 | to the `ceph-users mailing list <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com/>`_. |