Hello Sir/Madam, We are facing the serious problem for our proxmox with Ceph. I have already submitted the ticket to Proxmox but they said that only option trying to recover the mondb.We would like to know any some suggestion in our situation. So far the only option that I see would be in trying to recover the mondb from an OSD. But this action is usually a last resort. Since I don't know the outcome, the cluster could then very well be dead and thus all data lost. https://docs.ceph.com/docs/luminous/rados/troubleshooting/troubleshooting-m… --- Sadly this didn't have any effect either. But I think I found a clue to what might be going on. # ceph-osd.0.log 2020-03-24 21:22:06.462100 7fb33aab0e00 10 osd.0 0 read_superblock sb(e8e81549-91e5-4370-b091-9500f406a2b2 osd.0 0bb2b9bb-9a70-4d6f-8d4e-3fc5049d63d6 e14334 [13578,14334] lci=[0,14334]) # ceph-mon.cccs01.log 2020-03-24 21:26:48.038345 7f7ef791a700 10 mon.cccs01(a)0(leader).osd e14299 e14299: 48 total, 13 up, 35 in 2020-03-24 21:26:48.038351 7f7ef791a700 5 mon.cccs01(a)0(leader).osd e14299 can_mark_out current in_ratio 0.729167 < min 0.75, will not mark osds out 2020-03-24 21:26:48.038360 7f7ef791a700 10 mon.cccs01(a)0(leader).osd e14299 tick NOOUT flag set, not checking down osds 2020-03-24 21:26:48.038364 7f7ef791a700 10 mon.cccs01(a)0(leader).osd e14299 min_last_epoch_clean 0 # ceph-mon.cccs06.log 2020-03-22 22:26:57.056939 7f3c1993a700 1 mon.cccs06(a)5(peon).osd e14333 e14333: 48 total, 48 up, 48 in 2020-03-22 22:27:04.113054 7f3c1993a700 0 mon.cccs06@5(peon) e31 handle_command mon_command({"prefix":"df","format":"json"} v 0) v1 2020-03-22 22:27:04.113086 7f3c1993a700 0 log_channel(audit) log [DBG] : from='client.? 10.1.14.8:0/4265796352' entity='client.admin' cmd=[{"prefix":"df","format":"json"}]: dispatch 2020-03-22 22:27:09.752027 7f3c1993a700 1 mon.cccs06(a)5(peon).osd e14334 e14334: 48 total, 48 up, 48 in ... 2020-03-23 10:42:51.891722 7ff1d9079700 0 mon.cccs06(a)2(synchronizing).osd e14269 crush map has features 288514051259236352, adjusting msgr requires 2020-03-23 10:42:51.891729 7ff1d9079700 0 mon.cccs06(a)2(synchronizing).osd e14269 crush map has features 288514051259236352, adjusting msgr requires 2020-03-23 10:42:51.891730 7ff1d9079700 0 mon.cccs06(a)2(synchronizing).osd e14269 crush map has features 1009089991638532096, adjusting msgr requires 2020-03-23 10:42:51.891732 7ff1d9079700 0 mon.cccs06(a)2(synchronizing).osd e14269 crush map has features 288514051259236352, adjusting msgr requires It seems that the OSD have a epoch of e14334 but the MONs seems to have e14269 for the OSDs. I could only find the e14334 on the ceph-mon.cccs06. The cccs06 has been the last MON standing (the node also reset). But when the cluster came back the MONs with the old epoch came up first and joined. The syslog showed that these were the last log entries written. So the nodes reset shortly after. This would fit to cccs06 being the last MON alive. # cccs01 Mar 22 22:16:09 cccs01 pmxcfs[2502]: [dcdb] notice: leader is 1/2502 Mar 22 22:16:09 cccs01 pmxcfs[2502]: [dcdb] notice: synced members: 1/2502, 5/2219 # cccs02 Mar 22 22:15:57 cccs02 pmxcfs[2514]: [dcdb] notice: we (3/2514) left the process group Mar 22 22:15:57 cccs02 pmxcfs[2514]: [dcdb] crit: leaving CPG group # cccs06 Mar 22 22:31:16 cccs06 pmxcfs[2662]: [status] noMar 22 22:34:01 cccs06 systemd-modules-load[773]: Inserted module 'iscsi_tcp' Mar 22 22:34:01 cccs06 systemd-modules-load[773]: Inserted module 'ib_iser' There must have been some issue prior to the reset as I found those error messages. They could explain why no older epoch was written anymore. # cccs01 2020-03-22 22:22:15.661060 7fc09c85c100 -1 rocksdb: IO error: /var/lib/ceph/mon/ceph-cccs01/store.db/LOCK: Permission denied 2020-03-22 22:22:15.661067 7fc09c85c100 -1 error opening mon data directory at '/var/lib/ceph/mon/ceph-cccs01': (22) Invalid argument # cccs02 2020-03-22 22:31:11.209524 7fd034786100 -1 rocksdb: IO error: /var/lib/ceph/mon/ceph-cccs02/store.db/LOCK: Permission denied 2020-03-22 22:31:11.209541 7fd034786100 -1 error opening mon data directory at '/var/lib/ceph/mon/ceph-cccs02': (22) Invalid argument # cccs06 no such entries. From my point of view, the last question is now: How to get the epoch from the OSD into the MON DB. I have no answer to this yet. 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