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1 | =========================================== |
2 | Hard Disk and File System Recommendations | |
3 | =========================================== | |
4 | ||
5 | .. index:: hard drive preparation | |
6 | ||
7 | Hard Drive Prep | |
8 | =============== | |
9 | ||
10 | Ceph aims for data safety, which means that when the :term:`Ceph Client` | |
11 | receives notice that data was written to a storage drive, that data was actually | |
12 | written to the storage drive. For old kernels (<2.6.33), disable the write cache | |
13 | if the journal is on a raw drive. Newer kernels should work fine. | |
14 | ||
15 | Use ``hdparm`` to disable write caching on the hard disk:: | |
16 | ||
17 | sudo hdparm -W 0 /dev/hda 0 | |
18 | ||
19 | In production environments, we recommend running a :term:`Ceph OSD Daemon` with | |
20 | separate drives for the operating system and the data. If you run data and an | |
21 | operating system on a single disk, we recommend creating a separate partition | |
22 | for your data. | |
23 | ||
24 | .. index:: filesystems | |
25 | ||
26 | Filesystems | |
27 | =========== | |
28 | ||
29 | Ceph OSD Daemons rely heavily upon the stability and performance of the | |
30 | underlying filesystem. | |
31 | ||
32 | Recommended | |
33 | ----------- | |
34 | ||
35 | We currently recommend ``XFS`` for production deployments. | |
36 | ||
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37 | Not recommended |
38 | --------------- | |
39 | ||
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40 | We recommand *against* using ``btrfs`` due to the lack of a stable |
41 | version to test against and frequent bugs in the ENOSPC handling. | |
42 | ||
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43 | We recommend *against* using ``ext4`` due to limitations in the size |
44 | of xattrs it can store, and the problems this causes with the way Ceph | |
45 | handles long RADOS object names. Although these issues will generally | |
46 | not surface with Ceph clusters using only short object names (e.g., an | |
47 | RBD workload that does not include long RBD image names), other users | |
48 | like RGW make extensive use of long object names and can break. | |
49 | ||
50 | Starting with the Jewel release, the ``ceph-osd`` daemon will refuse | |
51 | to start if the configured max object name cannot be safely stored on | |
52 | ``ext4``. If the cluster is only being used with short object names | |
53 | (e.g., RBD only), you can continue using ``ext4`` by setting the | |
54 | following configuration option:: | |
55 | ||
56 | osd max object name len = 256 | |
57 | osd max object namespace len = 64 | |
58 | ||
59 | .. note:: This may result in difficult-to-diagnose errors if you try | |
60 | to use RGW or other librados clients that do not properly | |
61 | handle or politely surface any resulting ENAMETOOLONG | |
62 | errors. |