Good thought. The storage for the monitor data is a RAID-0 over three NVMe devices. Watching iostat, they are completely idle, maybe 0.8% to 1.4% for a second every minute or so. ---------------- Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1 On Thu, Apr 8, 2021 at 7:48 PM Zizon Qiu <zzdtsv@xxxxxxxxx> wrote: > > Will it be related to some kind of disk issue of that mon located in,which may casually > slow down IO and further the rocksdb? > > > On Fri, Apr 9, 2021 at 4:29 AM Robert LeBlanc <robert@xxxxxxxxxxxxx> wrote: >> >> I found this thread that matches a lot of what I'm seeing. I see the >> ms_dispatch thread going to 100%, but I'm at a single MON, the >> recovery is done and the rocksdb MON database is ~300MB. I've tried >> all the settings mentioned in that thread with no noticeable >> improvement. I was hoping that once the recovery was done (backfills >> to reformatted OSDs) that it would clear up, but not yet. So any other >> ideas would be really helpful. Our MDS is functioning, but stalls a >> lot because the mons miss heartbeats. >> >> mon_compact_on_start = true >> rocksdb_cache_size = 1342177280 >> mon_lease = 30 >> mon_osd_cache_size = 200000 >> mon_sync_max_payload_size = 4096 >> >> ---------------- >> Robert LeBlanc >> PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1 >> >> On Thu, Apr 8, 2021 at 1:11 PM Stefan Kooman <stefan@xxxxxx> wrote: >> > >> > On 4/8/21 6:22 PM, Robert LeBlanc wrote: >> > > I upgraded our Luminous cluster to Nautilus a couple of weeks ago and >> > > converted the last batch of FileStore OSDs to BlueStore about 36 hours >> > > ago. Yesterday our monitor cluster went nuts and started constantly >> > > calling elections because monitor nodes were at 100% and wouldn't >> > > respond to heartbeats. I reduced the monitor cluster to one to prevent >> > > the constant elections and that let the system limp along until the >> > > backfills finished. There are large amounts of time where ceph commands >> > > hang with the CPU is at 100%, when the CPU drops I see a lot of work >> > > getting done in the monitor logs which stops as soon as the CPU is at >> > > 100% again. >> > >> > >> > Try reducing mon_sync_max_payload_size=4096. I have seen Frank Schilder >> > advise this several times because of monitor issues. Also recently for a >> > cluster that got upgraded from Luminous -> Mimic -> Nautilus. >> > >> > Worth a shot. >> > >> > Otherwise I'll try to look in depth and see if I can come up with >> > something smart (for now I need to go catch some sleep). >> > >> > Gr. Stefan
