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73 lines
2.3 KiB
ReStructuredText
73 lines
2.3 KiB
ReStructuredText
===================
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Ceph Block Device
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===================
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.. index:: Ceph Block Device; introduction
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A block is a sequence of bytes (often 512).
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Block-based storage interfaces are a mature and common way to store data on
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media including HDDs, SSDs, CDs, floppy disks, and even tape.
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The ubiquity of block device interfaces is a perfect fit for interacting
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with mass data storage including Ceph.
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Ceph block devices are thin-provisioned, resizable, and store data striped over
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multiple OSDs. Ceph block devices leverage
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:abbr:`RADOS (Reliable Autonomic Distributed Object Store)` capabilities
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including snapshotting, replication and strong consistency. Ceph block
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storage clients communicate with Ceph clusters through kernel modules or
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the ``librbd`` library.
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.. ditaa::
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+------------------------+ +------------------------+
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| Kernel Module | | librbd |
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+------------------------+-+------------------------+
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| RADOS Protocol |
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+------------------------+-+------------------------+
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| OSDs | | Monitors |
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+------------------------+ +------------------------+
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.. note:: Kernel modules can use Linux page caching. For ``librbd``-based
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applications, Ceph supports `RBD Caching`_.
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Ceph's block devices deliver high performance with vast scalability to
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`kernel modules`_, or to :abbr:`KVMs (kernel virtual machines)` such as `QEMU`_, and
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cloud-based computing systems like `OpenStack`_ and `CloudStack`_ that rely on
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libvirt and QEMU to integrate with Ceph block devices. You can use the same cluster
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to operate the :ref:`Ceph RADOS Gateway <object-gateway>`, the
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:ref:`Ceph File System <ceph-file-system>`, and Ceph block devices simultaneously.
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.. important:: To use Ceph Block Devices, you must have access to a running
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Ceph cluster.
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.. toctree::
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:maxdepth: 1
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Basic Commands <rados-rbd-cmds>
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.. toctree::
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:maxdepth: 2
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Operations <rbd-operations>
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.. toctree::
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:maxdepth: 2
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Integrations <rbd-integrations>
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.. toctree::
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:maxdepth: 2
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Manpages <man/index>
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.. toctree::
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:maxdepth: 2
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APIs <api/index>
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.. _RBD Caching: ./rbd-config-ref/
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.. _kernel modules: ./rbd-ko/
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.. _QEMU: ./qemu-rbd/
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.. _OpenStack: ./rbd-openstack
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.. _CloudStack: ./rbd-cloudstack
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