[ceph.git] / ceph / doc / rbd / index.rst

===================
 Ceph Block Device
===================

.. index:: Ceph Block Device; introduction

A block is a sequence of bytes (for example, a 512-byte block of data).
Block-based storage interfaces are the most common way to store data with
rotating media such as hard disks, CDs, floppy disks, and even traditional
9-track tape. The ubiquity of block device interfaces makes a virtual block
device an ideal candidate to interact with a mass data storage system like Ceph.

Ceph block devices are thin-provisioned, resizable and store data striped over
multiple OSDs in a Ceph cluster.  Ceph block devices leverage
:abbr:`RADOS (Reliable Autonomic Distributed Object Store)` capabilities
such as snapshotting, replication and consistency. Ceph's
:abbr:`RADOS (Reliable Autonomic Distributed Object Store)` Block Devices (RBD)
interact with OSDs using kernel modules or the ``librbd`` library.

.. ditaa::  +------------------------+ +------------------------+
            |     Kernel Module      | |        librbd          |
            +------------------------+-+------------------------+
            |                   RADOS Protocol                  |
            +------------------------+-+------------------------+
            |          OSDs          | |        Monitors        |
            +------------------------+ +------------------------+

.. note:: Kernel modules can use Linux page caching. For ``librbd``-based
   applications, Ceph supports `RBD Caching`_.

Ceph's block devices deliver high performance with infinite scalability to
`kernel modules`_, or to :abbr:`KVMs (kernel virtual machines)` such as `QEMU`_, and
cloud-based computing systems like `OpenStack`_ and `CloudStack`_ that rely on
libvirt and QEMU to integrate with Ceph block devices. You can use the same cluster
to operate the :ref:`Ceph RADOS Gateway <object-gateway>`, the
:ref:`CephFS filesystem <ceph-filesystem>`, and Ceph block devices simultaneously.

.. important:: To use Ceph Block Devices, you must have access to a running
   Ceph cluster.

.. toctree::
	:maxdepth: 1

	Commands <rados-rbd-cmds>
	Kernel Modules <rbd-ko>
	Snapshots<rbd-snapshot>
	Mirroring <rbd-mirroring>
	LIO iSCSI Gateway <iscsi-overview>
	QEMU <qemu-rbd>
	libvirt <libvirt>
	Cache Settings <rbd-config-ref/>
	OpenStack <rbd-openstack>
	CloudStack <rbd-cloudstack>
	RBD Replay <rbd-replay>

.. toctree::
	:maxdepth: 2

	Manpages <man/index>

.. toctree::
	:maxdepth: 2

	APIs <api/index>

.. _RBD Caching: ./rbd-config-ref/
.. _kernel modules: ./rbd-ko/
.. _QEMU: ./qemu-rbd/
.. _OpenStack: ./rbd-openstack
.. _CloudStack: ./rbd-cloudstack
Commit	Line	Data
7c673cae FG	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
181888fb FG	16	such as snapshotting, replication and consistency. Ceph's
181888fb FG	17	:abbr:`RADOS (Reliable Autonomic Distributed Object Store)` Block Devices (RBD)
7c673cae FG	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
181888fb	28	.. note:: Kernel modules can use Linux page caching. For ``librbd``-based
7c673cae FG	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
91327a77 AA	35	to operate the :ref:`Ceph RADOS Gateway <object-gateway>`, the
91327a77 AA	36	:ref:`CephFS filesystem <ceph-filesystem>`, and Ceph block devices simultaneously.
7c673cae	37
181888fb	38	.. important:: To use Ceph Block Devices, you must have access to a running
7c673cae FG	39	Ceph cluster.
	40
	41	.. toctree::
	42	:maxdepth: 1
	43
	44	Commands <rados-rbd-cmds>
	45	Kernel Modules <rbd-ko>
	46	Snapshots<rbd-snapshot>
181888fb	47	Mirroring <rbd-mirroring>
b32b8144	48	LIO iSCSI Gateway <iscsi-overview>
7c673cae FG	49	QEMU <qemu-rbd>
	50	libvirt <libvirt>
	51	Cache Settings <rbd-config-ref/>
	52	OpenStack <rbd-openstack>
	53	CloudStack <rbd-cloudstack>
7c673cae	54	RBD Replay <rbd-replay>
d2e6a577 FG	55
	56	.. toctree::
	57	:maxdepth: 2
	58
	59	Manpages <man/index>
	60
	61	.. toctree::
	62	:maxdepth: 2
	63
	64	APIs <api/index>
	65
91327a77 AA	66	.. _RBD Caching: ./rbd-config-ref/
	67	.. _kernel modules: ./rbd-ko/
	68	.. _QEMU: ./qemu-rbd/
	69	.. _OpenStack: ./rbd-openstack
	70	.. _CloudStack: ./rbd-cloudstack