projects / ceph.git / blame
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| 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 | |
| 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/ |