ceph/doc/rados/configuration/filesystem-recommendations.rst

   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
  37 Not recommended
  38 ---------------
  39
  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
  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.