Recover the Ceph Monitor Store Using OSDs

Introduction ¶ A few weeks ago I helped a Ceph user to recover his broken cluster (see this thread ). Basically, after his Monitors stopped working he re-deployed a new cluster with the same Ceph FSID and attached the existing OSDs to the re-deployed hosts. But it’s not that easy to re-activate those OSDs because the new Monitors don’t have the old osdmap, hence they don’t know anything about the existing OSDs.