On Mon, Nov 16, 2015 at 4:20 PM, Sage Weil <sage@xxxxxxxxxxxx> wrote: > On Mon, 16 Nov 2015, Dan van der Ster wrote: >> Instead of keeping a 24hr loadavg, how about we allow scrubs whenever >> the loadavg is decreasing (or below the threshold)? As long as the >> 1min loadavg is less than the 15min loadavg, we should be ok to allow >> new scrubs. If you agree I'll add the patch below to my PR. > > I like the simplicity of that, I'm afraid its going to just trigger a > feedback loop and oscillations on the host. I.e., as soo as we see *any* > decrease, all osds on the host will start to scrub, which will push the > load up. Once that round of PGs finish, the load will start to drop > again, triggering another round. This'll happen regardless of whether > we're in the peak hours or not, and the high-level goal (IMO at least) is > to do scrubbing in non-peak hours. We checked our OSDs' 24hr loadavg plots today and found that the original idea of 0.8 * 24hr loadavg wouldn't leave many chances for scrubs to run. So maybe if we used 0.9 or 1.0 it would be doable. BTW, I realized there was a silly error in that earlier patch, and we anyway need an upper bound, say # cpus. So until your response came I was working with this idea: https://stikked.web.cern.ch/stikked/view/raw/5586a912 -- dan -- 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
