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- This commit adds a link to the "Create a Ceph File System" page. The link that it adds is to the "Adding a data pool to the MDS" subsection of the file layouts page. - s/mds/file system/ Fixes: https://tracker.ceph.com/issues/48531 Signed-off-by: Zac Dover <zac.dover@gmail.com>
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99 lines
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=========================
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Create a Ceph file system
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=========================
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Creating pools
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==============
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A Ceph file system requires at least two RADOS pools, one for data and one for metadata.
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When configuring these pools, you might consider:
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- Using a higher replication level for the metadata pool, as any data loss in
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this pool can render the whole file system inaccessible.
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- Using lower-latency storage such as SSDs for the metadata pool, as this will
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directly affect the observed latency of file system operations on clients.
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- The data pool used to create the file system is the "default" data pool and
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the location for storing all inode backtrace information, used for hard link
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management and disaster recovery. For this reason, all inodes created in
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CephFS have at least one object in the default data pool. If erasure-coded
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pools are planned for the file system, it is usually better to use a
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replicated pool for the default data pool to improve small-object write and
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read performance for updating backtraces. Separately, another erasure-coded
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data pool can be added (see also :ref:`ecpool`) that can be used on an entire
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hierarchy of directories and files (see also :ref:`file-layouts`).
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Refer to :doc:`/rados/operations/pools` to learn more about managing pools. For
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example, to create two pools with default settings for use with a file system, you
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might run the following commands:
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.. code:: bash
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$ ceph osd pool create cephfs_data
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$ ceph osd pool create cephfs_metadata
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Generally, the metadata pool will have at most a few gigabytes of data. For
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this reason, a smaller PG count is usually recommended. 64 or 128 is commonly
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used in practice for large clusters.
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.. note:: The names of the file systems, metadata pools, and data pools can
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only have characters in the set [a-zA-Z0-9\_-.].
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Creating a file system
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======================
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Once the pools are created, you may enable the file system using the ``fs new`` command:
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.. code:: bash
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$ ceph fs new <fs_name> <metadata> <data>
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For example:
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.. code:: bash
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$ ceph fs new cephfs cephfs_metadata cephfs_data
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$ ceph fs ls
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name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs_data ]
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Once a file system has been created, your MDS(s) will be able to enter
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an *active* state. For example, in a single MDS system:
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.. code:: bash
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$ ceph mds stat
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cephfs-1/1/1 up {0=a=up:active}
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Once the file system is created and the MDS is active, you are ready to mount
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the file system. If you have created more than one file system, you will
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choose which to use when mounting.
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- `Mount CephFS`_
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- `Mount CephFS as FUSE`_
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.. _Mount CephFS: ../../cephfs/mount-using-kernel-driver
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.. _Mount CephFS as FUSE: ../../cephfs/mount-using-fuse
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If you have created more than one file system, and a client does not
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specify a file system when mounting, you can control which file system
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they will see by using the `ceph fs set-default` command.
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Adding a Data Pool to the File System
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-------------------------------------
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See :ref:`adding-data-pool-to-file-system`.
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Using Erasure Coded pools with CephFS
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=====================================
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You may use Erasure Coded pools as CephFS data pools as long as they have overwrites enabled, which is done as follows:
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.. code:: bash
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ceph osd pool set my_ec_pool allow_ec_overwrites true
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Note that EC overwrites are only supported when using OSDS with the BlueStore backend.
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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.
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