On Wed, May 12, 2021 at 10:10:45AM +0300, Mykola Golub wrote: > > So, the current behavior is: In `PrimaryLogPG::recover_backfill`, due > > to the "unfound" oid is not removed from `backfills_in_flight`, > > `next_backfill_to_complete` is always set to the "unfound" oid [4], > > and `new_last_backfill` is not updated any more pointing to the object > > before the "unfound" oid. The backfill still continues and terminates > > only after all objects are pulled/pushed, but "complete" position > > remains on the object before "unfound". After the backfill is finished > > the pg enters "backfill_unfound" state. When the pg is re-peered > > (e.g. after restarting an osd) it enters "backfilling" state starting > > the backfill from "unfound" oid position, detects the "unfound" object > > again, scans the remaining objects detecting they are already copied, > > and enters "backfill_unfound" state again with the same "complete" > > position on the "unfound" object. > > > > This looks like a reasonable behavoir to me, and the only problem is > > that reported assertion failure, which probably is just needed to be > > removed? > > https://github.com/ceph/ceph/pull/41270 This PR is merged. Thanks! And "backfill_unfound" state is not reset after a non-primary OSD restart. But it is still possible to reset the state to clean when the primary osd is restarted. I will re-describe the situation. Suppose we have a 2+1 EC pool, and an object is missing 2 shards on both non-primary osds. We initiate backfill by setting a non-primary osd out. During the backfill the primary osd detects the missing shards and the pg enters "backfill_unfound" state, the last_backfill position is properly set to the object before the "unfound" (in post-nautilus, for nautilus I opened [1] to make it work). If re-peering occurs due to a non-primary osd is restarted, the backfill is restarted from the last_backfill position and the "unfound" object is detected again. But if re-peering occurs due the primary osd is temporarily stopped (restarted), another non-primary osd becomes primary and "drives" the backfill from the last_backfill position, and as the shard is missing here it is just skipped from the backfill, the missing object is not detected and the pg enters clean state. Is there something that can/should be improved here? It is rather unfortunate that the information about missing object is lost on the restart (until scrub or next backfill). On the other hand the situation when we have many shards are missing for an object is rather unlikely. Also, if for example it happened that the shard was missing on the primary it would not even be detected on backfill. [1] https://github.com/ceph/ceph/pull/41293 -- Mykola Golub _______________________________________________ Dev mailing list -- dev@xxxxxxx To unsubscribe send an email to dev-leave@xxxxxxx
