Hi Mark, I don¹t suppose you logged latency during those tests, did you? I¹m one of the folks, as Bryan mentioned, that advocates turning these values down. I¹m okay with extending recovery time, especially when we are talking about a default of 3x replication, with the trade off of better client response.
-- Warren Wang On 6/1/15, 12:43 PM, "Mark Nelson" <mnel...@redhat.com> wrote: >On 05/29/2015 04:47 PM, Samuel Just wrote: >> Many people have reported that they need to lower the osd recovery >>config options to minimize the impact of recovery on client io. We are >>talking about changing the defaults as follows: >> >> osd_max_backfills to 1 (from 10) >> osd_recovery_max_active to 3 (from 15) >> osd_recovery_op_priority to 1 (from 10) >> osd_recovery_max_single_start to 1 (from 5) >> >> We'd like a bit of feedback first though. Is anyone happy with the >>current configs? Is anyone using something between these values and the >>current defaults? What kind of workload? I'd guess that lowering >>osd_max_backfills to 1 is probably a good idea, but I wonder whether >>lowering osd_recovery_max_active and osd_recovery_max_single_start will >>cause small objects to recover unacceptably slowly. >> >> Thoughts? > >We ran recovery tests last year around when firefly was released. The >basic gist of it was that as you increase client IO, the ratio of >backfill to client IO changes for a given combination of priority >settings. IE you can tune around 10 15 10 5, or 1 3 1 1, but in each >case the ratio of client to recovery IO appears to scale with the amount >of client IO, even past the super saturation point. I believe users >will have a hard time finding optimal settings as clusters at the >saturation point will behave differently than those in heavy >super-saturation. > > >http://nhm.ceph.com/Ceph_3XRep_Backfill_Recovery_Results.pdf >http://nhm.ceph.com/Ceph_62EC_Backfill_Recovery_Results.pdf >_______________________________________________ >ceph-users mailing list >ceph-users@lists.ceph.com >http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
