ceph/doc/cephfs/createfs.rst

   1 ========================
   2 Create a Ceph filesystem
   3 ========================
   4
   5 Creating pools
   6 ==============
   7
   8 A Ceph filesystem requires at least two RADOS pools, one for data and one for metadata.
   9 When configuring these pools, you might consider:
  10
  11 - Using a higher replication level for the metadata pool, as any data
  12   loss in this pool can render the whole filesystem inaccessible.
  13 - Using lower-latency storage such as SSDs for the metadata pool, as this
  14   will directly affect the observed latency of filesystem operations
  15   on clients.
  16
  17 Refer to :doc:`/rados/operations/pools` to learn more about managing pools.  For
  18 example, to create two pools with default settings for use with a filesystem, you
  19 might run the following commands:
  20
  21 .. code:: bash
  22
  23     $ ceph osd pool create cephfs_data <pg_num>
  24     $ ceph osd pool create cephfs_metadata <pg_num>
  25
  26 Creating a filesystem
  27 =====================
  28
  29 Once the pools are created, you may enable the filesystem using the ``fs new`` command:
  30
  31 .. code:: bash
  32
  33     $ ceph fs new <fs_name> <metadata> <data>
  34
  35 For example:
  36
  37 .. code:: bash
  38
  39     $ ceph fs new cephfs cephfs_metadata cephfs_data
  40     $ ceph fs ls
  41     name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs_data ]
  42
  43 Once a filesystem has been created, your MDS(s) will be able to enter
  44 an *active* state.  For example, in a single MDS system:
  45
  46 .. code:: bash
  47
  48     $ ceph mds stat
  49     cephfs-1/1/1 up {0=a=up:active}
  50
  51 Once the filesystem is created and the MDS is active, you are ready to mount
  52 the filesystem.  If you have created more than one filesystem, you will
  53 choose which to use when mounting.
  54
  55         - `Mount CephFS`_
  56         - `Mount CephFS as FUSE`_
  57
  58 .. _Mount CephFS: ../../cephfs/kernel
  59 .. _Mount CephFS as FUSE: ../../cephfs/fuse
  60
  61 If you have created more than one filesystem, and a client does not
  62 specify a filesystem when mounting, you can control which filesystem
  63 they will see by using the `ceph fs set-default` command.
  64
  65 Using Erasure Coded pools with CephFS
  66 =====================================
  67
  68 You may use Erasure Coded pools as CephFS data pools as long as they have overwrites enabled, which is done as follows:
  69
  70 .. code:: bash
  71
  72     ceph osd pool set my_ec_pool allow_ec_overwrites true
  73
  74 Note that EC overwrites are only supported when using OSDS with the BlueStore backend.
  75
  76 You may not use Erasure Coded pools as CephFS metadata pools, because CephFS metadata is stored using RADOS *OMAP* data structures, which EC pools cannot store.
  77