No latency spikes seen the last 24 hours after manually compacting all the OSDs so it seemed to solve it for us at least. Thanks all. Mvh. Torkil On 23-03-2024 12:32, Torkil Svensgaard wrote:
Hi guys
Thanks for the suggestions, we'll do the offline compaction and see how big an impact it will have.
Even if compact-on-iteration should take care of it, doing it offline should avoid I/O problems during the compaction, correct? That's why offline is preferred to online?
Mvh.
Torkil
On 22-03-2024 16:47, Joshua Baergen wrote:
Personally, I don't think the compaction is actually required. Reef has compact-on-iteration enabled, which should take care of this automatically. We see this sort of delay pretty often during PG cleaning, at the end of a PG being cleaned, when the PG has a high count of objects, whether or not OSD compaction has been keeping up with tombstones. It's unfortunately just something to ride through these days until backfill completes.
https://github.com/ceph/ceph/pull/49438 is a recent attempt to improve things in this area, but I'm not sure whether it would eliminate this issue. We've considered going to higher PG counts (and thus fewer objects per PG) as a possible mitigation as well.
Josh
On Fri, Mar 22, 2024 at 2:59 AM Alexander E. Patrakov <patrakov@gmail.com> wrote:
Hello Torkil,
The easiest way (in my opinion) to perform offline compaction is a bit different than what Igor suggested. We had a prior off-list conversation indicating that the results would be equivalent.
1. ceph config set osd osd_compact_on_start true 2. Restart the OSD that you want to compact (or the whole host at once, if you want to compact the whole host and your failure domain allows for that) 3. ceph config set osd osd_compact_on_start false
The OSD will restart, but will not show as "up" until the compaction process completes. In your case, I would expect it to take up to 40 minutes.
On Fri, Mar 22, 2024 at 3:46 PM Torkil Svensgaard <torkil@drcmr.dk> wrote:
On 22-03-2024 08:38, Igor Fedotov wrote:
Hi Torkil,
Hi Igor
highly likely you're facing a well known issue with RocksDB performance drop after bulk data removal. The latter might occur at source OSDs after PG migration completion.
Aha, thanks.
You might want to use DB compaction (preferably offline one using ceph- kvstore-tool) to get OSD out of this "degraded" state or as a preventive measure. I'd recommend to do that for all the OSDs right now. And once again after rebalancing is completed. This should improve things but unfortunately no 100% guarantee.
Why is offline preferred? With offline the easiest way would be something like stop all OSDs one host at a time and run a loop over /var/lib/ceph/$id/osd.*?
Also curious if you have DB/WAL on fast (SSD or NVMe) drives? This might be crucial..
We do, 22 HDDs and 2 DB/WAL NVMes pr host.
Thanks.
Mvh.
Torkil
Thanks,
Igor
On 3/22/2024 9:59 AM, Torkil Svensgaard wrote:
Good morning,
Cephadm Reef 18.2.1. We recently added 4 hosts and changed a failure domain from host to datacenter which is the reason for the large misplaced percentage.
We were seeing some pretty crazy spikes in "OSD Read Latencies" and "OSD Write Latencies" on the dashboard. Most of the time everything is well but then for periods of time, 1-4 hours, latencies will go to 10+ seconds for one or more OSDs. This also happens outside scrub hours and it is not the same OSDs every time. The OSDs affected are HDD with DB/WAL on NVMe.
Log snippet:
" ... 2024-03-22T06:48:22.859+0000 7fb184b52700 1 heartbeat_map is_healthy 'OSD::osd_op_tp thread 0x7fb169898700' had timed out after 15.000000954s 2024-03-22T06:48:22.859+0000 7fb185b54700 1 heartbeat_map is_healthy 'OSD::osd_op_tp thread 0x7fb169898700' had timed out after 15.000000954s 2024-03-22T06:48:22.864+0000 7fb169898700 1 heartbeat_map clear_timeout 'OSD::osd_op_tp thread 0x7fb169898700' had timed out after 15.000000954s 2024-03-22T06:48:22.864+0000 7fb169898700 0 bluestore(/var/lib/ceph/ osd/ceph-112) log_latency slow operation observed for submit_transact, latency = 17.716707230s 2024-03-22T06:48:22.880+0000 7fb1748ae700 0 bluestore(/var/lib/ceph/ osd/ceph-112) log_latency_fn slow operation observed for _txc_committed_kv, latency = 17.732601166s, txc = 0x55a5bcda0f00 2024-03-22T06:48:38.077+0000 7fb184b52700 1 heartbeat_map is_healthy 'OSD::osd_op_tp thread 0x7fb169898700' had timed out after 15.000000954s 2024-03-22T06:48:38.077+0000 7fb184b52700 1 heartbeat_map is_healthy 'OSD::osd_op_tp thread 0x7fb169898700' had timed out after 15.000000954s ... "
" [root@dopey ~]# ceph -s cluster: id: 8ee2d228-ed21-4580-8bbf-0649f229e21d health: HEALTH_WARN 1 failed cephadm daemon(s) Low space hindering backfill (add storage if this doesn't resolve itself): 1 pg backfill_toofull
services: mon: 5 daemons, quorum lazy,jolly,happy,dopey,sleepy (age 3d) mgr: jolly.tpgixt(active, since 10d), standbys: dopey.lxajvk, lazy.xuhetq mds: 1/1 daemons up, 2 standby osd: 540 osds: 539 up (since 6m), 539 in (since 15h); 6250 remapped pgs
data: volumes: 1/1 healthy pools: 15 pools, 10849 pgs objects: 546.35M objects, 1.1 PiB usage: 1.9 PiB used, 2.3 PiB / 4.2 PiB avail pgs: 1425479651/3163081036 objects misplaced (45.066%) 6224 active+remapped+backfill_wait 4516 active+clean 67 active+clean+scrubbing 25 active+remapped+backfilling 16 active+clean+scrubbing+deep 1 active+remapped+backfill_wait+backfill_toofull
io: client: 117 MiB/s rd, 68 MiB/s wr, 274 op/s rd, 183 op/s wr recovery: 438 MiB/s, 192 objects/s "
Anyone know what the issue might be? Given that is happens on and off with large periods of time in between with normal low latencies I think it unlikely that it is just because the cluster is busy.
Also, how come there's only a small amount of PGs doing backfill when we have such a large misplaced percentage? Can this be just from backfill reservation logjam?
Mvh.
Torkil
-- Torkil Svensgaard Systems Administrator Danish Research Centre for Magnetic Resonance DRCMR, Section 714 Copenhagen University Hospital Amager and Hvidovre Kettegaard Allé 30, 2650 Hvidovre, Denmark _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
-- Alexander E. Patrakov _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io
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-- Torkil Svensgaard Systems Administrator Danish Research Centre for Magnetic Resonance DRCMR, Section 714 Copenhagen University Hospital Amager and Hvidovre Kettegaard Allé 30, 2650 Hvidovre, Denmark