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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 | |
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16 | such as snapshotting, replication and consistency. Ceph's |
17 | :abbr:`RADOS (Reliable Autonomic Distributed Object Store)` Block Devices (RBD) | |
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18 | interact with OSDs using kernel modules or the ``librbd`` library. |
19 | ||
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20 | .. ditaa:: |
21 | ||
22 | +------------------------+ +------------------------+ | |
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23 | | Kernel Module | | librbd | |
24 | +------------------------+-+------------------------+ | |
25 | | RADOS Protocol | | |
26 | +------------------------+-+------------------------+ | |
27 | | OSDs | | Monitors | | |
28 | +------------------------+ +------------------------+ | |
29 | ||
181888fb | 30 | .. note:: Kernel modules can use Linux page caching. For ``librbd``-based |
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31 | applications, Ceph supports `RBD Caching`_. |
32 | ||
33 | Ceph's block devices deliver high performance with infinite 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 | |
91327a77 | 37 | to operate the :ref:`Ceph RADOS Gateway <object-gateway>`, the |
9f95a23c | 38 | :ref:`Ceph File System <ceph-file-system>`, and Ceph block devices simultaneously. |
7c673cae | 39 | |
181888fb | 40 | .. important:: To use Ceph Block Devices, you must have access to a running |
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41 | Ceph cluster. |
42 | ||
43 | .. toctree:: | |
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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> | |
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57 | |
58 | .. toctree:: | |
59 | :maxdepth: 2 | |
60 | ||
61 | Manpages <man/index> | |
62 | ||
63 | .. toctree:: | |
64 | :maxdepth: 2 | |
65 | ||
66 | APIs <api/index> | |
67 | ||
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68 | .. _RBD Caching: ./rbd-config-ref/ |
69 | .. _kernel modules: ./rbd-ko/ | |
70 | .. _QEMU: ./qemu-rbd/ | |
71 | .. _OpenStack: ./rbd-openstack | |
72 | .. _CloudStack: ./rbd-cloudstack |