2011/7/7 Trent W. Buck <twb-mailman-colle...@cyber.com.au>: > I rolled out collectd 4.8, running in each of about 20 LXC jails. The > I/O load was crippling the server, so I reduced polling with "Interval > 60" in each jail. > > However I would prefer to > > - poll every 10s (the default); > > - batch write RRDs, such that any given RRD is only written once > every ten minutes; and > > - distribute these writes more-or-less evenly over time, i.e. avoid a > huge I/O spike on the tenth minute. > > IIUC that means I should use this config: > > Interval 10 > CacheTimeout 600 > RandomTimeout 300 > > But this doesn't seem to be improving matters. Polling dm-25 (the > filesystem mounted at /var/lib/collectd) every ten seconds, before the > change: > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > dm-25 163.70 16.80 1292.80 168 12928 > dm-25 88.90 4.00 707.20 40 7072 > dm-25 279.20 8.80 2224.80 88 22248 > dm-25 302.40 8.80 2410.40 88 24104 > dm-25 122.40 7.20 972.00 72 9720 > dm-25 386.90 7.20 3088.00 72 30880 > > After the change: > > Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn > dm-25 33.20 11.20 254.40 112 2544 > dm-25 292.10 12.00 2324.80 120 23248 > dm-25 297.50 15.20 2364.80 152 23648 > dm-25 41.90 8.80 326.40 88 3264 > dm-25 428.30 4.00 3422.40 40 34224 > dm-25 283.60 4.80 2264.00 48 22640 > > Is that wrong, or am I just expecting too much of buffered rrd writes? > How many RRD files do you have ? You can try using WritesPerSecond option to limit amount of writes and CacheFlush to ensure no data older than X will be in cache, like that:
CacheFlush 1500 WritesPerSecond 20 > _______________________________________________ > collectd mailing list > collectd@verplant.org > http://mailman.verplant.org/listinfo/collectd > _______________________________________________ collectd mailing list collectd@verplant.org http://mailman.verplant.org/listinfo/collectd