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55 lines
1.9 KiB
ReStructuredText
.. _cephfs-multifs:
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Multiple Ceph File Systems
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==========================
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Beginning with the Pacific release, multiple file system support is stable
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and ready to use. This functionality allows configuring separate file systems
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with full data separation on separate pools.
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Existing clusters must set a flag to enable multiple file systems::
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ceph fs flag set enable_multiple true
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New Ceph clusters automatically set this.
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Creating a new Ceph File System
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-------------------------------
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The new ``volumes`` plugin interface (see: :doc:`/cephfs/fs-volumes`) automates
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most of the work of configuring a new file system. The "volume" concept is
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simply a new file system. This can be done via::
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ceph fs volume create <fs_name>
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Ceph will create the new pools and automate the deployment of new MDS to
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support the new file system. The deployment technology used, e.g. cephadm, will
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also configure the MDS affinity (see: :ref:`mds-join-fs`) of new MDS daemons to
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operate the new file system.
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Securing access
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---------------
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The ``fs authorize`` command allows configuring the client's access to a
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particular file system. See also in :ref:`fs-authorize-multifs`. The client will
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only have visibility of authorized file systems and the Monitors/MDS will
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reject access to clients without authorization.
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Other Notes
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-----------
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Multiple file systems do not share pools. This is particularly important for
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snapshots but also because no measures are in place to prevent duplicate
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inodes. The Ceph commands prevent this dangerous configuration.
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Each file system has its own set of MDS ranks. Consequently, each new file
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system requires more MDS daemons to operate and increases operational costs.
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This can be useful for increasing metadata throughput by application or user
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base but also adds cost to the creation of a file system. Generally, a single
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file system with subtree pinning is a better choice for isolating load between
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applications.
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