Hi Sagara, looks like your situation is more complex. Before doing anything potentially destructive, you need to investigate some more. A possible interpretation (numbering just for the example):
OSD 0 PG at version 1 OSD 1 PG at version 2 OSD 2 PG has scrub error Depending on the version of the PG on OSD 2, either OSD 0 needs to roll forward (OSD 2 PG at version 2), or OSD 1 needs to roll back (OSD 2 PG at version 1). Part of the relevant information on OSD 2 seems to be unreadable, therefore pg repair bails out. You need to find out if you are in this situation or some other case. If you are, you need to find out somehow if you need to roll back or forward. I'm afraid in your current situation, even taking the OSD with the scrub errors down will not rebuild the PG. I would probably try: - find out with smartctl if the OSD with scrub errors is in a pre-fail state (has remapped sectors) - if it is: * take it down and try to make a full copy with ddrescue * if ddrescure manages to copy everything, copy back to a new disk and add to ceph * if ddrescue fails to copy everything, you could try if badblocks manages to get the disk back; ddrescue can force remappings of broken sectors (non-destructive read-write check) and it can happen that data becomes readable again, exchange the disk as soon as possible thereafter - if the disk is healthy: * try to find out if you can deduce the state of the copies on every OSD The tool for low-level operations is bluestore-tool. I never used it, so you need to look at the documentation. If everything fails, I guess your last option is to decide for one of the copies, export it from one OSD and inject it to another one (but not any of 0,1,2!). This will establish 2 identical copies and the third one will be changed to this one automatically. Note that this may lead to data loss on objects that were in the undefined state. As far as I can see, its only 1 object and probably possible to recover from (backup, snapshot). Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Sagara Wijetunga <sagara...@yahoo.com> Sent: 01 November 2020 14:05:36 To: ceph-users@ceph.io Subject: [ceph-users] Re: How to recover from active+clean+inconsistent+failed_repair? Hi Frank Thanks for the reply. > I think this happens when a PG has 3 different copies and cannot decide which > one is correct. You might have hit a very rare case. You should start with > the scrub errors, check which PGs and which copies (OSDs) are affected. It > sounds almost like all 3 scrub errors are on the same PG. Yes, all 3 errors are for the same PG and on the same OSD: 2020-11-01 18:25:09.333339 osd.0 [ERR] 3.b shard 2 soid 3:d577e975:::1000023675e.00000000:head : candidate had a missing snapset key, candidate had a missing info key 2020-11-01 18:25:09.333342 osd.0 [ERR] 3.b soid 3:d577e975:::1000023675e.00000000:head : failed to pick suitable object info 2020-11-01 18:26:33.496255 osd.0 [ERR] 3.b repair 3 errors, 0 fixed > You might have had a combination of crash and OSD fail, your situation is > probably not covered by "single point of failure". Yes it was a complex crash, all went down. > In case you have a PG with scrub errors on 2 copies, you should be able to > reconstruct the PG from the third with PG export/PG import commands. I have not done a PG export/import before. Mind if you could send the instructions or a link for it. Thanks Sagara _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-le...@ceph.io _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-le...@ceph.io
