We've run into this issue on the first two clusters after upgrading them to Nautilus (14.2.2). When marking a single OSD back in to the cluster some PGs will switch to the active+remapped+backfill_wait+backfill_toofull state for a while and then it goes away after some of the other PGs finish backfilling. This is rather odd because all the data on the cluster could fit on a single drive, but we have over 100 of them: # ceph -s cluster: id: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX health: HEALTH_ERR Degraded data redundancy (low space): 1 pg backfill_toofull services: mon: 3 daemons, quorum a1cephmon002,a1cephmon003,a1cephmon004 (age 21h) mgr: a1cephmon002(active, since 21h), standbys: a1cephmon003, a1cephmon004 mds: cephfs:2 {0=a1cephmon002=up:active,1=a1cephmon003=up:active} 1 up:standby osd: 143 osds: 142 up, 142 in; 106 remapped pgs rgw: 11 daemons active (radosgw.a1cephrgw008, radosgw.a1cephrgw009, radosgw.a1cephrgw010, radosgw.a1cephrgw011, radosgw.a1tcephrgw002, radosgw.a1tcephrgw003, radosgw.a1tcephrgw004, radosgw.a1tcephrgw005, radosgw.a1tcephrgw006, radosgw.a1tcephrgw007, radosgw.a1tcephrgw008) data: pools: 19 pools, 5264 pgs objects: 1.45M objects, 148 GiB usage: 658 GiB used, 436 TiB / 437 TiB avail pgs: 44484/4351770 objects misplaced (1.022%) 5158 active+clean 104 active+remapped+backfill_wait 1 active+remapped+backfilling 1 active+remapped+backfill_wait+backfill_toofull io: client: 19 MiB/s rd, 13 MiB/s wr, 431 op/s rd, 509 op/s wr I searched the archives, but most of the other people had more full clusters where sometimes this state could be valid. This bug report seems similar, but the fix was just to make it a warning instead of an error: https://tracker.ceph.com/issues/39555 So I've created a new tracker ticket to troubleshoot this issue: https://tracker.ceph.com/issues/4125 Let me know what you guys think, Bryan