Hello! We are in the process of expanding our CEPH cluster (by both adding OSD hosts and replacing smaller-sized HDDs on our existing hosts). So far we have gone host by host, removing the old OSDs, swapping the physical HDDs, and re-adding them. This process has gone smooth, aside from one issue: upon any action taken on the cluster (adding new OSDs, replacing old, etc), we have PGs get stuck "activating"which causes around 3.5% of PGs go inactive, causing IO to stop. Here is a current look at our ceph -s command: cluster: id: e8ffe2eb-f8fc-4110-a4bc-1715e878fb7b health: HEALTH_WARN Reduced data availability: 166 pgs inactive Degraded data redundancy: 137153907/3658405707 objects degraded (3.749%), 930 pgs degraded, 928 pgs undersized 10 pgs not deep-scrubbed in time 33709 slow ops, oldest one blocked for 35956 sec, daemons [osd.103,osd.104,osd.105,osd.106,osd.107,osd.109,osd.111,osd.112,osd.113,osd.114]... have slow ops. services: mon: 3 daemons, quorum lb3,lb2,lb1 (age 8w) mgr: lb1(active, since 6w), standbys: lb3, lb2 osd: 117 osds: 117 up (since 15m), 117 in (since 10h); 2033 remapped pgs rgw: 3 daemons active (lb1.rgw0, lb2.rgw0, lb3.rgw0) task status: data: pools: 8 pools, 5793 pgs objects: 609.74M objects, 169 TiB usage: 308 TiB used, 430 TiB / 738 TiB avail pgs: 2.866% pgs not active 137153907/3658405707 objects degraded (3.749%) 262215404/3658405707 objects misplaced (7.167%) 3754 active+clean 963 active+remapped+backfill_wait 892 active+undersized+degraded+remapped+backfill_wait 136 activating+remapped 27 activating+undersized+degraded+remapped 8 active+undersized+degraded+remapped+backfilling 6 active+clean+scrubbing+deep 3 activating+degraded+remapped 3 active+remapped+backfilling 1 active+undersized+remapped+backfill_wait io: client: 94 KiB/s rd, 94 op/s rd, 0 op/s wr recovery: 112 MiB/s, 372 objects/s progress: Rebalancing after osd.20 marked in (10h) [............................] (remaining: 11d) Rebalancing after osd.41 marked in (10h) [=...........................] (remaining: 8d) Rebalancing after osd.30 marked in (10h) [=...........................] (remaining: 9d) Rebalancing after osd.1 marked in (10h) [=======.....................] (remaining: 2h) Rebalancing after osd.10 marked in (10h) [............................] (remaining: 12d) Rebalancing after osd.50 marked in (10h) [............................] (remaining: 2w) Rebalancing after osd.71 marked out (10h) [==..........................] (remaining: 5d) What you may find interesting is the "slow ops" warnings. This is where our inactive PGs become stuck. Once the cluster gets into this state, I'm able to recover IO usually by restarting the OSDs with slow ops. However, what's extremely strange, is this workaround only works after about 12 hours since the last OSD addition. Restarting the slow ops OSDs before roughly 12 hours results in the slow ops returning immediately. Our first thought was hardware issues, however we ruled this out after the slow ops warnings appeared on brand new HDDs and OSD hosts. Monitoring the IO saturation of the OSDs reporting slow ops shows actual usage nowhere near saturation, and no hardware issues are present on the drives themselves. Looking at the journalctl logs of one of the affected OSDs above, we see the following repeated multiple times: osd.103 56934 get_health_metrics reporting 2 slow ops, oldest is osd_op(client.467952.0:1520304537 8.6fbs0 8.1e6826fb (undecoded) ondisk+retry+write+known_if_redirected e56923 So far my procedure for the disk swaps have been as follows: 1. Set noout,norebalance, and norecover on the cluster. 2. Use ceph-ansible to remove the old disk OSD IDs 3. Swap physical HDDs, re-add with ceph-ansible 4. Unset noout,norebalance,norecover I should note this issue appears even with simple OSD additions (not removals), as we added 2 brand new hosts to the cluster and saw the same issue. I've been trying to think of any possible cause of this issue, I should mention our cluster is messy at the moment hardware-wise (we have a mix of 7T HDDs, 4T HDDs, and 10T HDDs - moving to all 10T HDDs but the process to swap has been taking a while). One warning I've noticed during the old disk removals is a warning about too many PGs per OSD, however this warning clears once the new OSDs are added, which is to be expected I assume. If anyone would be willing to provide any hints of where to look, it would be much appreciated! Thanks for your time. -- Justin Goetz Systems Engineer, TeraSwitch Inc. jgoetz@teraswitch.com 412-945-7045 (NOC) | 412-459-7945 (Direct)