ceph/doc/rbd/rbd.rst

   1 ===================
   2  Ceph Block Device
   3 ===================
   4
   5 .. index:: Ceph Block Device; introduction
   6
   7 A block is a sequence of bytes (for example, a 512-byte block of data).
   8 Block-based storage interfaces are the most common way to store data with
   9 rotating media such as hard disks, CDs, floppy disks, and even traditional
  10 9-track tape. The ubiquity of block device interfaces makes a virtual block
  11 device an ideal candidate to interact with a mass data storage system like Ceph.
  12
  13 Ceph block devices are thin-provisioned, resizable and store data striped over
  14 multiple OSDs in a Ceph cluster.  Ceph block devices leverage
  15 :abbr:`RADOS (Reliable Autonomic Distributed Object Store)` capabilities
  16 such as snapshotting, replication and consistency. Ceph's
  17 :abbr:`RADOS (Reliable Autonomic Distributed Object Store)` Block Devices (RBD)
  18 interact with OSDs using kernel modules or the ``librbd`` library.
  19
  20 .. ditaa::  +------------------------+ +------------------------+
  21             |     Kernel Module      | |        librbd          |
  22             +------------------------+-+------------------------+
  23             |                   RADOS Protocol                  |
  24             +------------------------+-+------------------------+
  25             |          OSDs          | |        Monitors        |
  26             +------------------------+ +------------------------+
  27
  28 .. note:: Kernel modules can use Linux page caching. For ``librbd``-based
  29    applications, Ceph supports `RBD Caching`_.
  30
  31 Ceph's block devices deliver high performance with infinite scalability to
  32 `kernel modules`_, or to :abbr:`KVMs (kernel virtual machines)` such as `QEMU`_, and
  33 cloud-based computing systems like `OpenStack`_ and `CloudStack`_ that rely on
  34 libvirt and QEMU to integrate with Ceph block devices. You can use the same cluster
  35 to operate the `Ceph RADOS Gateway`_, the `Ceph FS filesystem`_, and Ceph block
  36 devices simultaneously.
  37
  38 .. important:: To use Ceph Block Devices, you must have access to a running
  39    Ceph cluster.
  40
  41 .. toctree::
  42         :maxdepth: 1
  43
  44         Commands <rados-rbd-cmds>
  45         Kernel Modules <rbd-ko>
  46         Snapshots<rbd-snapshot>
  47         Mirroring <rbd-mirroring>
  48         QEMU <qemu-rbd>
  49         libvirt <libvirt>
  50         Cache Settings <rbd-config-ref/>
  51         OpenStack <rbd-openstack>
  52         CloudStack <rbd-cloudstack>
  53         Manpage rbd <../../man/8/rbd>
  54         Manpage rbd-fuse <../../man/8/rbd-fuse>
  55         Manpage rbd-nbd <../../man/8/rbd-nbd>
  56         Manpage ceph-rbdnamer <../../man/8/ceph-rbdnamer>
  57         RBD Replay <rbd-replay>
  58         Manpage rbd-replay-prep <../../man/8/rbd-replay-prep>
  59         Manpage rbd-replay <../../man/8/rbd-replay>
  60         Manpage rbd-replay-many <../../man/8/rbd-replay-many>
  61         Manpage rbdmap <../../man/8/rbdmap>
  62         librbd <librbdpy>
  63
  64
  65
  66 .. _RBD Caching: ../rbd-config-ref/
  67 .. _kernel modules: ../rbd-ko/
  68 .. _QEMU: ../qemu-rbd/
  69 .. _OpenStack: ../rbd-openstack
  70 .. _CloudStack: ../rbd-cloudstack
  71 .. _Ceph RADOS Gateway: ../../radosgw/
  72 .. _Ceph FS filesystem: ../../cephfs/