Ceph Block Device

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 withrotating media such as hard disks, CDs, floppy disks, and even traditional9-track tape. The ubiquity of block device interfaces makes a virtual blockdevice an ideal candidate to interact with a mass data storage system like Ceph.

Ceph block devices are thin-provisioned, resizable and store data striped overmultiple OSDs in a Ceph cluster. Ceph block devices leverageRADOS capabilitiessuch as snapshotting, replication and consistency. Ceph’sRADOS Block Devices (RBD)interact with OSDs using kernel modules or the librbd library.

Ceph Block Device - 图1

Note

Kernel modules can use Linux page caching. For librbd-basedapplications, Ceph supports RBD Caching.

Ceph’s block devices deliver high performance with infinite scalability tokernel modules, or to KVMs such as QEMU, andcloud-based computing systems like OpenStack and CloudStack that rely onlibvirt and QEMU to integrate with Ceph block devices. You can use the same clusterto operate the Ceph RADOS Gateway, theCeph File System, and Ceph block devices simultaneously.

Important

To use Ceph Block Devices, you must have access to a runningCeph cluster.