The ceph-volume tool aims to be a single purpose command line tool to deploy logical volumes as OSDs, trying to maintain a similar API to ceph-disk when preparing, activating, and creating OSDs.

It deviates from ceph-disk by not interacting or relying on the udev rules that come installed for Ceph. These rules allow automatic detection of previously setup devices that are in turn fed into ceph-disk to activate them.

ceph-volume lvm

By making use of LVM tags, the lvm sub-command is able to store and later re-discover and query devices associated with OSDs so that they can later activated. This includes support for lvm-based technologies like dm-cache as well.

For ceph-volume, the use of dm-cache is transparent, there is no difference for the tool, and it treats dm-cache like a plain logical volume.