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208 lines
5.4 KiB
ReStructuredText
208 lines
5.4 KiB
ReStructuredText
.. _ceph-file-system:
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=================
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Ceph File System
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=================
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The Ceph File System, or **CephFS**, is a POSIX-compliant file system built on
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top of Ceph's distributed object store, **RADOS**. CephFS endeavors to provide
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a state-of-the-art, multi-use, highly available, and performant file store for
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a variety of applications, including traditional use-cases like shared home
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directories, HPC scratch space, and distributed workflow shared storage.
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CephFS achieves these goals through the use of some novel architectural
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choices. Notably, file metadata is stored in a separate RADOS pool from file
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data and served via a resizable cluster of *Metadata Servers*, or **MDS**,
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which may scale to support higher throughput metadata workloads. Clients of
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the file system have direct access to RADOS for reading and writing file data
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blocks. For this reason, workloads may linearly scale with the size of the
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underlying RADOS object store; that is, there is no gateway or broker mediating
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data I/O for clients.
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Access to data is coordinated through the cluster of MDS which serve as
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authorities for the state of the distributed metadata cache cooperatively
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maintained by clients and MDS. Mutations to metadata are aggregated by each MDS
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into a series of efficient writes to a journal on RADOS; no metadata state is
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stored locally by the MDS. This model allows for coherent and rapid
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collaboration between clients within the context of a POSIX file system.
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.. image:: cephfs-architecture.svg
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CephFS is the subject of numerous academic papers for its novel designs and
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contributions to file system research. It is the oldest storage interface in
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Ceph and was once the primary use-case for RADOS. Now it is joined by two
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other storage interfaces to form a modern unified storage system: RBD (Ceph
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Block Devices) and RGW (Ceph Object Storage Gateway).
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Getting Started with CephFS
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^^^^^^^^^^^^^^^^^^^^^^^^^^^
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For most deployments of Ceph, setting up a CephFS file system is as simple as:
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.. code:: bash
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ceph fs volume create <fs name>
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The Ceph `Orchestrator`_ will automatically create and configure MDS for
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your file system if the back-end deployment technology supports it (see
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`Orchestrator deployment table`_). Otherwise, please `deploy MDS manually
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as needed`_.
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Finally, to mount CephFS on your client nodes, see `Mount CephFS:
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Prerequisites`_ page. Additionally, a command-line shell utility is available
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for interactive access or scripting via the `cephfs-shell`_.
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.. _Orchestrator: ../mgr/orchestrator
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.. _deploy MDS manually as needed: add-remove-mds
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.. _Orchestrator deployment table: ../mgr/orchestrator/#current-implementation-status
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.. _Mount CephFS\: Prerequisites: mount-prerequisites
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.. _cephfs-shell: cephfs-shell
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.. raw:: html
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<!---
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Administration
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^^^^^^^^^^^^^^
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.. raw:: html
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--->
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.. toctree::
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:maxdepth: 1
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:hidden:
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Create a CephFS file system <createfs>
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Administrative commands <administration>
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Provision/Add/Remove MDS(s) <add-remove-mds>
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MDS failover and standby configuration <standby>
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MDS Cache Size Limits <cache-size-limits>
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MDS Configuration Settings <mds-config-ref>
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Manual: ceph-mds <../../man/8/ceph-mds>
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Export over NFS <nfs>
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Export over NFS with volume nfs interface <fs-nfs-exports>
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Application best practices <app-best-practices>
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FS volume and subvolumes <fs-volumes>
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CephFS Quotas <quota>
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Health messages <health-messages>
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Upgrading old file systems <upgrading>
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.. raw:: html
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<!---
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Mounting CephFS
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^^^^^^^^^^^^^^^
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.. raw:: html
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--->
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.. toctree::
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:maxdepth: 1
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:hidden:
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Client Configuration Settings <client-config-ref>
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Client Authentication <client-auth>
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Mount CephFS: Prerequisites <mount-prerequisites>
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Mount CephFS using Kernel Driver <mount-using-kernel-driver>
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Mount CephFS using FUSE <mount-using-fuse>
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Use the CephFS Shell <cephfs-shell>
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Supported Features of Kernel Driver <kernel-features>
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Manual: ceph-fuse <../../man/8/ceph-fuse>
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Manual: mount.ceph <../../man/8/mount.ceph>
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Manual: mount.fuse.ceph <../../man/8/mount.fuse.ceph>
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.. raw:: html
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<!---
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CephFS Concepts
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^^^^^^^^^^^^^^^
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.. raw:: html
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--->
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.. toctree::
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:maxdepth: 1
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:hidden:
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MDS States <mds-states>
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POSIX compatibility <posix>
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MDS Journaling <mds-journaling>
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File layouts <file-layouts>
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Distributed Metadata Cache <mdcache>
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Dynamic Metadata Management in CephFS <dynamic-metadata-management>
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CephFS IO Path <cephfs-io-path>
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LazyIO <lazyio>
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Directory fragmentation <dirfrags>
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Multiple active MDS daemons <multimds>
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.. raw:: html
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<!---
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Troubleshooting and Disaster Recovery
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.. raw:: html
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--->
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.. toctree::
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:hidden:
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Client eviction <eviction>
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Scrubbing the File System <scrub>
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Handling full file systems <full>
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Metadata repair <disaster-recovery-experts>
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Troubleshooting <troubleshooting>
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Disaster recovery <disaster-recovery>
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cephfs-journal-tool <cephfs-journal-tool>
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.. raw:: html
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<!---
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Developer Guides
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^^^^^^^^^^^^^^^^
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.. raw:: html
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--->
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.. toctree::
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:maxdepth: 1
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:hidden:
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Journaler Configuration <journaler>
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Client's Capabilities <capabilities>
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Java and Python bindings <api/index>
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Mantle <mantle>
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.. raw:: html
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<!---
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Additional Details
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^^^^^^^^^^^^^^^^^^
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.. raw:: html
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--->
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.. toctree::
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:maxdepth: 1
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:hidden:
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Experimental Features <experimental-features>
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