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38 lines
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ReStructuredText
38 lines
1.4 KiB
ReStructuredText
===============
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Block Devices
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===============
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A block is a sequence of bytes (for example, a 512-byte block of data).
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Block-based storage interfaces are the most common way to store data with
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rotating media such as hard disks, CDs, floppy disks, and even traditional
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9-track tape. The ubiquity of block device interfaces makes a virtual block
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device an ideal candidate to interact with a mass data storage system like Ceph.
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Ceph's RADOS Block Devices (RBD) interact with RADOS OSDs using the
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``librados`` and ``librbd`` libraries. RBDs are thin-provisioned, resizable
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and store data striped over multiple OSDs in a Ceph cluster. RBDs inherit
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``librados`` capabilities such as snapshotting and cloning. Ceph's RBDs deliver
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high performance with infinite scalability to kernel objects, kernel virtual
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machines and cloud-based computing systems like OpenStack and CloudStack.
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The ``librbd`` library converts data blocks into objects for storage in
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RADOS OSD clusters--the same storage system for ``librados`` object stores and
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the Ceph FS filesystem. You can use the same cluster to operate object stores,
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the Ceph FS filesystem, and RADOS block devices simultaneously.
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.. important:: To use RBD, you must have a running Ceph cluster.
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.. toctree::
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:maxdepth: 1
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RADOS Commands <rados-rbd-cmds>
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Kernel Objects <rbd-ko>
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RBD Snapshots <rbd-snapshot>
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QEMU and RBD <qemu-rbd>
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libvirt <libvirt>
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RBD and OpenStack <rbd-openstack>
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