On Thu, May 7, 2020 at 6:22 AM Yan, Zheng <ukernel@xxxxxxxxx> wrote: > On Thu, May 7, 2020 at 1:27 AM Patrick Donnelly <pdonnell@xxxxxxxxxx> > wrote: > > > > Hello Robert, > > > > On Mon, Mar 9, 2020 at 7:55 PM Robert Ruge <robert.ruge@xxxxxxxxxxxxx> > wrote: > > > For a 1.1PB raw cephfs system currently storing 191TB of data and 390 > million objects (mostly small Python, ML training files etc.) how many MDS > servers should I be running? > > > > > > System is Nautilus 14.2.8. > > > > > > > > > > > > I ask because up to know I have run one MDS with one standby-replay > and occasionally it blows up with large memory consumption, 60Gb+ even > though I have mds_cache_memory_limit = 32G and that was 16G until recently. > It of course tries to restart on another MDS node fails again and after > several attempts usually comes back up. Today I increased to two active > MDS’s but the question is what is the optimal number for a pretty active > system? The single MDS seemed to regularly run around 1400 req/s and I > often get up to six clients failing to respond to cache pressure. > > > > Ideally, the only reason you should add more active MDS (increase > > max_mds) is because you want to increase request throughput. > > > > 60GB RSS is not completely unexpected. A 32GB cache size would use > > approximately 48GB (150%) RSS in a steady state situation. You may > > ahve hit some kind of bug as others have reported which is causing the > > cache size / anonymous memory to continually increase. You will need > > to post more information about the client type/version, cache usage, > > perf dumps, and workload to help diagnose. > > > > > https://github.com/ceph/ceph/pull/34571 may help if "ceph daemon mds.a > dump_mempools" shows buffer_anon uses lots of memory. > We struggle with cache management as well and I just thought it was due to our really old kernel clients (I'm sure that doesn't help). I'll keep an eye on the buffer_anon. Looks like that is dumped in perf dump so I can go back and look through graphite data for it. ---------------- Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1 _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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