Ceph » CephFS

In the scenario where the monitor databases are lost and must be rebuilt, the file system will need recreated. (Assuming pools have been recovered by OSDMap reconstruction from the incremental OSDMaps on the OSDs.) Some external projects like ceph-csi reasonably expect the fscid to be stable. During this recovery scenario, the fscid will likely change back to the default starting value (0 or 1).

Allow the administrator to set the fscid via the "fs new" command. If no existing file system exists with that fscid, allow it. (This breaks the "rule" that fscids for "new" file systems are always increasing. We should note this exception in the documentation!)