Ceph File System

The Ceph File System interface creates virtual file systems and stores them as a series of objects within pools. Ceph assigns these objects to placement groups and distributes or places them pseudo-randomly in OSDs throughout the cluster.

Typically, the Ceph File System uses two pools:

• Metadata: The metadata pool stores the data of the Ceph Metadata Server (MDS), which generally consists of inodes; that is, the file ownership, permissions, creation date and time, last modified or accessed date and time, parent directory, and so on.

• Data: The data pool stores file data. Ceph may store a file as one or more objects, typically representing smaller chunks of file data such as extents.

Depending upon the application consuming the Ceph File System interface, usually OpenStack Platform, users may create, modify, and delete files in a Ceph File System. Ceph handles the create, retrieve, update, and delete operations of each individual object representing the file.

Deleting files destroys the corresponding objects in an unrecoverable manner. However, residual data artifacts may continue to reside on storage media until overwritten. Data may also remain in backup archives.