I use CFQ but I have just discovered it completely _kills_ writes when also reading (doing backfill for example)
If I run a fio job for synchronous writes and at the same time run a fio job for random reads, writes drop to 10 IOPS (oops!). Setting io priority with ionice works nicely maintaining ~250 IOPS for writes while throttling reads. I looked at osd_disk_thread_ioprio_class - for some reason documentation says “idle” “rt” “be” for possible values, but it only accepts numbers (3 should be idle) in my case - and doesn’t seem to do anything in regards to slow requests. Do I need to restart the OSD for it to take effect? It actually looks like it made things even worse for me… Changing the scheduler to deadline improves the bottom line a a lot for my benchmark, but large amount of reads can still drop that to 30 IOPS - contrary to CFQ which maintains steady 250 IOPS for writes even under read load. What would be the recommendation here? Did someone test this extensively before? thanks Jan _______________________________________________ ceph-users mailing list [email protected] http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
