ceph/doc/rbd/index.rst

   1 ===================
   2  Ceph Block Device
   3 ===================
   4
   5 .. index:: Ceph Block Device; introduction
   6
   7 A block is a sequence of bytes (often 512).
   8 Block-based storage interfaces are a mature and common way to store data on
   9 media including HDDs, SSDs, CDs, floppy disks, and even tape.
  10 The ubiquity of block device interfaces is a perfect fit for interacting
  11 with mass data storage including Ceph.
  12
  13 Ceph block devices are thin-provisioned, resizable, and store data striped over
  14 multiple OSDs.  Ceph block devices leverage
  15 :abbr:`RADOS (Reliable Autonomic Distributed Object Store)` capabilities
  16 including snapshotting, replication and strong consistency. Ceph block
  17 storage clients communicate with Ceph clusters through kernel modules or
  18 the ``librbd`` library.
  19
  20 .. ditaa::
  21
  22             +------------------------+ +------------------------+
  23             |     Kernel Module      | |        librbd          |
  24             +------------------------+-+------------------------+
  25             |                   RADOS Protocol                  |
  26             +------------------------+-+------------------------+
  27             |          OSDs          | |        Monitors        |
  28             +------------------------+ +------------------------+
  29
  30 .. note:: Kernel modules can use Linux page caching. For ``librbd``-based
  31    applications, Ceph supports `RBD Caching`_.
  32
  33 Ceph's block devices deliver high performance with vast scalability to
  34 `kernel modules`_, or to :abbr:`KVMs (kernel virtual machines)` such as `QEMU`_, and
  35 cloud-based computing systems like `OpenStack`_ and `CloudStack`_ that rely on
  36 libvirt and QEMU to integrate with Ceph block devices. You can use the same cluster
  37 to operate the :ref:`Ceph RADOS Gateway <object-gateway>`, the
  38 :ref:`Ceph File System <ceph-file-system>`, and Ceph block devices simultaneously.
  39
  40 .. important:: To use Ceph Block Devices, you must have access to a running
  41    Ceph cluster.
  42
  43 .. toctree::
  44         :maxdepth: 1
  45
  46         Basic Commands <rados-rbd-cmds>
  47
  48 .. toctree::
  49         :maxdepth: 2
  50
  51         Operations <rbd-operations>
  52
  53 .. toctree::
  54         :maxdepth: 2
  55
  56         Integrations <rbd-integrations>
  57
  58 .. toctree::
  59         :maxdepth: 2
  60
  61         Manpages <man/index>
  62
  63 .. toctree::
  64         :maxdepth: 2
  65
  66         APIs <api/index>
  67
  68 .. _RBD Caching: ./rbd-config-ref/
  69 .. _kernel modules: ./rbd-ko/
  70 .. _QEMU: ./qemu-rbd/
  71 .. _OpenStack: ./rbd-openstack
  72 .. _CloudStack: ./rbd-cloudstack