I'm experimenting with single-host Ceph use cases, where HA is not important but data durability is. How does a Ceph cluster react to its (sole) mon being rolled back to an earlier state? The idea here is that the mon storage may not be redundant but would be (atomically, e.g. lvm snapshot and dump) backed up, say, daily. If the cluster goes down and then is brought back up with a mon backup that is several days to hours old, while the OSDs are up to date, what are the potential consequences? Of course I expect maintenance operations to be affected (obviously any OSDs added/removed would likely get confused). But what about regular operation? Things like snapshots and snapshot ranges. Is this likely to cause data loss, or would the OSDs and clients largely not be affected as long as the cluster config has not changed? There's a way of rebuilding the monmap from OSD data: http://docs.ceph.com/docs/mimic/rados/troubleshooting/troubleshooting-mon/#recovery-using-osds Would this be preferable to just restoring the mon from a backup? What about the MDS map? -- Hector Martin (hector@xxxxxxxxxxxxxx) Public Key: https://mrcn.st/pub _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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