Hi 19.2.2 with WPQ, osd-max-backfills and osd-recovery-max-active are set to 1. In order to get our PG sizes better aligned we doubled the number of PGs on the pool with the largest PG size. The pool is HDD with DB/WAL on SATA SSD and HDD sizes between 2TB and 20TB and PG size was ~140GB before the doubling. All went well but looking at this: " cluster: id: health: HEALTH_OK services: mon: 5 daemons, quorum ceph-flash1,ceph-flash2,ceph-flash3,ceph-e3s2,ceph-e3s3 (age 2d) mgr: ceph-flash2.utlhuz(active, since 4d), standbys: ceph-flash3.ciudre, ceph-flash1.erhakb mds: 1/1 daemons up, 2 standby osd: 576 osds: 576 up (since 2h), 576 in (since 3d); 8767 remapped pgs data: volumes: 1/1 healthy pools: 18 pools, 25249 pgs objects: 683.85M objects, 1.6 PiB usage: 2.7 PiB used, 1.9 PiB / 4.5 PiB avail pgs: 842769842/3951610673 objects misplaced (21.327%) 16481 active+clean 8762 active+remapped+backfill_wait 6 active+remapped+backfilling io: client: 374 MiB/s rd, 14 MiB/s wr, 2.86k op/s rd, 410 op/s wr recovery: 153 MiB/s, 38 objects/s " The balancer was running and seemingly making very small changes: " [root@lazy ~]# ceph balancer status { "active": true, "last_optimize_duration": "0:00:01.012679", "last_optimize_started": "Mon Apr 28 10:01:24 2025", "mode": "upmap", "no_optimization_needed": true, "optimize_result": "Optimization plan created successfully", "plans": [] } " I tried the pgremapper and that gave a nice throughput in the beginning but now it seems to be about back to scratch: " cluster: id: health: HEALTH_OK services: mon: 5 daemons, quorum ceph-flash1,ceph-flash2,ceph-flash3,ceph-e3s2,ceph-e3s3 (age 7h) mgr: ceph-flash2.utlhuz(active, since 5d), standbys: ceph-flash3.ciudre, ceph-flash1.erhakb mds: 1/1 daemons up, 2 standby osd: 577 osds: 577 up (since 5h), 577 in (since 31h); 7392 remapped pgs data: volumes: 1/1 healthy pools: 18 pools, 25249 pgs objects: 683.96M objects, 1.6 PiB usage: 2.7 PiB used, 1.9 PiB / 4.5 PiB avail pgs: 459889823/3952312686 objects misplaced (11.636%) 17857 active+clean 7384 active+remapped+backfill_wait 8 active+remapped+backfilling io: client: 70 MiB/s rd, 15 MiB/s wr, 689 op/s rd, 378 op/s wr recovery: 294 MiB/s, 75 objects/s " Balancer is still running and making small changes. This is going to take a while, any tips on how to escape the apparent bottleneck? Is having many PGs misplaced actually counter productive, so it would be better to throttle via target_max_misplaced_ratio? I was thinking it was better to let the balancer balance all it could, as that would make all the moves available and decrease the risk of bottlenecking. Thanks. Mvh. Torkil -- Torkil Svensgaard Sysadmin MR-Forskningssektionen, afs. 714 DRCMR, Danish Research Centre for Magnetic Resonance Hvidovre Hospital Kettegård Allé 30 DK-2650 Hvidovre Denmark Tel: +45 386 22828 E-mail: torkil@drcmr.dk