RBD mirroring is an asynchronous replication of RBD images between multiple Ceph clusters. RBD mirroring validates a point-in-time consistent replica of any change to an RBD image, including snapshots, clones, read and write IOPS and block device resizing. RBD mirroring can run in an active+active setup or an active+passive setup. RBD mirroring utilizes the RBD journaling and exclusive lock features which enables the RBD image to record all changes to the image in order of which they occur. These features validate that a crash-consistent copy of the remote image is available locally. Before mirroring can be enabled on a Ceph cluster the journaling feature must be enabled on the RBD image.
The daemon responsible for ensuring point-in-time consistency from one Ceph cluster to the other is the rbd-mirror daemon. Depending on your...