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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 | ||
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 |
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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 | ||
181888fb | 38 | .. important:: To use Ceph Block Devices, you must have access to a running |
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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> |
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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> |
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55 | |
56 | .. toctree:: | |
57 | :maxdepth: 2 | |
58 | ||
59 | Manpages <man/index> | |
60 | ||
61 | .. toctree:: | |
62 | :maxdepth: 2 | |
63 | ||
64 | APIs <api/index> | |
65 | ||
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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/ |