On Fri, Aug 30, 2013 at 9:44 PM, Mike Dawson <mike.dawson@xxxxxxxxxxxx> wrote: > Andrey, > > I use all the defaults: > > # ceph --admin-daemon /var/run/ceph/ceph-osd.1.asok config show | grep scrub > "osd_scrub_thread_timeout": "60", > "osd_scrub_finalize_thread_timeout": "600", > "osd_max_scrubs": "1", This one. I may suggest to increase max_interval and write some kind of script doing per-pg scrub with low intensity, so you`ll have one scrubbing PG or less anytime and you may wait some time before scrubbing next, so they will not start scrubbing at once when max_interval will expire. I had discussed some throttling mechanisms to scrubbing some months ago here or in ceph-devel, but there still no such implementation (it is ultimately low-priority task since it can be handled by such simple thing as proposal above). > "osd_scrub_load_threshold": "0.5", > "osd_scrub_min_interval": "86400", > "osd_scrub_max_interval": "604800", > "osd_scrub_chunk_min": "5", > "osd_scrub_chunk_max": "25", > "osd_deep_scrub_interval": "604800", > "osd_deep_scrub_stride": "524288", > > Which value are you referring to? > > > Does anyone know exactly how "osd scrub load threshold" works? The manual > states "The maximum CPU load. Ceph will not scrub when the CPU load is > higher than this number. Default is 50%." So on a system with multiple > processors and cores...what happens? Is the threshold .5 load (meaning half > a core) or 50% of max load meaning anything less than 8 if you have 16 > cores? > > Thanks, > Mike Dawson > > > On 8/30/2013 1:34 PM, Andrey Korolyov wrote: >> >> You may want to reduce scrubbing pgs per osd to 1 using config option >> and check the results. >> >> On Fri, Aug 30, 2013 at 8:03 PM, Mike Dawson <mike.dawson@xxxxxxxxxxxx> >> wrote: >>> >>> We've been struggling with an issue of spikes of high i/o latency with >>> qemu/rbd guests. As we've been chasing this bug, we've greatly improved >>> the >>> methods we use to monitor our infrastructure. >>> >>> It appears that our RBD performance chokes in two situations: >>> >>> - Deep-Scrub >>> - Backfill/recovery >>> >>> In this email, I want to focus on deep-scrub. Graphing '% Util' from >>> 'iostat >>> -x' on my hosts with OSDs, I can see Deep-Scrub take my disks from around >>> 10% utilized to complete saturation during a scrub. >>> >>> RBD writeback cache appears to cover the issue nicely, but occasionally >>> suffers drops in performance (presumably when it flushes). But, reads >>> appear >>> to suffer greatly, with multiple seconds of 0B/s of reads accomplished >>> (see >>> log fragment below). If I make the assumption that deep-scrub isn't >>> intended >>> to create massive spindle contention, this appears to be a problem. What >>> should happen here? >>> >>> Looking at the settings around deep-scrub, I don't see an obvious way to >>> say >>> "don't saturate my drives". Are there any setting in Ceph or otherwise >>> (readahead?) that might lower the burden of deep-scrub? >>> >>> If not, perhaps reads could be remapped to avoid waiting on saturated >>> disks >>> during scrub. >>> >>> Any ideas? >>> >>> 2013-08-30 15:47:20.166149 mon.0 [INF] pgmap v9853931: 20672 pgs: 20665 >>> active+clean, 7 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 5058KB/s wr, 217op/s >>> 2013-08-30 15:47:21.945948 mon.0 [INF] pgmap v9853932: 20672 pgs: 20665 >>> active+clean, 7 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 5553KB/s wr, 229op/s >>> 2013-08-30 15:47:23.205843 mon.0 [INF] pgmap v9853933: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 6580KB/s wr, 246op/s >>> 2013-08-30 15:47:24.843308 mon.0 [INF] pgmap v9853934: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 3795KB/s wr, 224op/s >>> 2013-08-30 15:47:25.862722 mon.0 [INF] pgmap v9853935: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 1414B/s rd, 3799KB/s wr, 181op/s >>> 2013-08-30 15:47:26.887516 mon.0 [INF] pgmap v9853936: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 1541B/s rd, 8138KB/s wr, 160op/s >>> 2013-08-30 15:47:27.933629 mon.0 [INF] pgmap v9853937: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 14458KB/s wr, 304op/s >>> 2013-08-30 15:47:29.127847 mon.0 [INF] pgmap v9853938: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 15300KB/s wr, 345op/s >>> 2013-08-30 15:47:30.344837 mon.0 [INF] pgmap v9853939: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 13128KB/s wr, 218op/s >>> 2013-08-30 15:47:31.380089 mon.0 [INF] pgmap v9853940: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 0B/s rd, 13299KB/s wr, 241op/s >>> 2013-08-30 15:47:32.388303 mon.0 [INF] pgmap v9853941: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 4951B/s rd, 8147KB/s wr, 192op/s >>> 2013-08-30 15:47:33.858382 mon.0 [INF] pgmap v9853942: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64556 GB / 174 TB avail; 7029B/s rd, 3254KB/s wr, 190op/s >>> 2013-08-30 15:47:35.279691 mon.0 [INF] pgmap v9853943: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 1651B/s rd, 2476KB/s wr, 207op/s >>> 2013-08-30 15:47:36.309078 mon.0 [INF] pgmap v9853944: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 3788KB/s wr, 239op/s >>> 2013-08-30 15:47:38.120343 mon.0 [INF] pgmap v9853945: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 4671KB/s wr, 239op/s >>> 2013-08-30 15:47:39.546980 mon.0 [INF] pgmap v9853946: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 13487KB/s wr, 444op/s >>> 2013-08-30 15:47:40.561203 mon.0 [INF] pgmap v9853947: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 15265KB/s wr, 489op/s >>> 2013-08-30 15:47:41.794355 mon.0 [INF] pgmap v9853948: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 7157KB/s wr, 240op/s >>> 2013-08-30 15:47:44.661000 mon.0 [INF] pgmap v9853949: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 4543KB/s wr, 204op/s >>> 2013-08-30 15:47:45.672198 mon.0 [INF] pgmap v9853950: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 3537KB/s wr, 221op/s >>> 2013-08-30 15:47:47.202776 mon.0 [INF] pgmap v9853951: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 0B/s rd, 5127KB/s wr, 312op/s >>> 2013-08-30 15:47:50.656948 mon.0 [INF] pgmap v9853952: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 32835B/s rd, 4996KB/s wr, 246op/s >>> 2013-08-30 15:47:53.165529 mon.0 [INF] pgmap v9853953: 20672 pgs: 20664 >>> active+clean, 8 active+clean+scrubbing+deep; 38136 GB data, 111 TB used, >>> 64555 GB / 174 TB avail; 33446B/s rd, 12064KB/s wr, 361op/s >>> >>> >>> -- >>> Thanks, >>> >>> Mike Dawson >>> Co-Founder & Director of Cloud Architecture >>> Cloudapt LLC >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
