Hello Robert, On Mon, Mar 9, 2020 at 7:55 PM Robert Ruge <robert.r...@deakin.edu.au> 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. -- Patrick Donnelly, Ph.D. He / Him / His Senior Software Engineer Red Hat Sunnyvale, CA GPG: 19F28A586F808C2402351B93C3301A3E258DD79D _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-le...@ceph.io
