Ceph Block Device
A block is a sequence of bytes (often 512). Block-based storage interfaces are a mature and common way to store data on media including HDDs, SSDs, CDs, floppy disks, and even tape. The ubiquity of block device interfaces is a perfect fit for interacting with mass data storage including Ceph.
Ceph block devices are thin-provisioned, resizable, and store data striped over
multiple OSDs. Ceph block devices leverage
RADOS capabilities
including snapshotting, replication and strong consistency. Ceph block
storage clients communicate with Ceph clusters through kernel modules or
the librbd library.
Note
Kernel modules can use Linux page caching. For librbd-based
applications, Ceph supports RBD Caching.
Ceph’s block devices deliver high performance with vast scalability to kernel modules, or to KVMs 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 Ceph RADOS Gateway, the Ceph File System, and Ceph block devices simultaneously.
Important
To use Ceph Block Devices, you must have access to a running Ceph cluster.