On Wed, Jan 29, 2020 at 1:25 AM Samy Ascha <samy@xxxxxx> wrote: > > Hi! > > I've been running CephFS for a while now and ever since setting it up, I've seen unexpectedly large write i/o on the CephFS metadata pool. > > The filesystem is otherwise stable and I'm seeing no usage issues. > > I'm in a read-intensive environment, from the clients' perspective and throughput for the metadata pool is consistently larger than that of the data pool. > > For example: > > # ceph osd pool stats > pool cephfs_data id 1 > client io 7.6 MiB/s rd, 19 KiB/s wr, 404 op/s rd, 1 op/s wr > > pool cephfs_metadata id 2 > client io 338 KiB/s rd, 43 MiB/s wr, 84 op/s rd, 26 op/s wr > > I realise, of course, that this is a momentary display of statistics, but I see this unbalanced r/w activity consistently when monitoring it live. > > I would like some insight into what may be causing this large imbalance in r/w, especially since I'm in a read-intensive (web hosting) environment. The MDS is still writing its journal and updating the "open file table". The MDS needs to record certain information about the state of its cache and the state issued to clients. Even if the clients aren't changing anything. (This is workload dependent but will be most obvious when clients are opening files _not_ in cache already.) -- Patrick Donnelly, Ph.D. He / Him / His Senior Software Engineer Red Hat Sunnyvale, CA GPG: 19F28A586F808C2402351B93C3301A3E258DD79D _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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