Hi, Am 02.12.2013 04:27, schrieb James Harper: >> Hi, >> >>>> The low points are all ~35Mbytes/sec and the high points are all >>>> ~60Mbytes/sec. This is very reproducible. >>> >>> It occurred to me that just stopping the OSD's selectively would allow me to >>> see if there was a change when one >>> was ejected, but at no time was there a change to the graph... >> >> did you configure the pool with 3 copies and try to run the benchmark test >> with one OSD only ? >> Can you reproduce the values for each OSD ? > > I'll have to do that after hours. I'm not seeing this across all VM's though > so I think it's a bit hit and miss (the graph is constant for that one VM > though). > > What I did do was to shut down each OSD selectively, and there was no change > to the graph. > > One thing I hadn't considered is that this VM is running on a physical host > which has a different network set up - using LACP across 2 ports. I suspect > that the combination of connections and the way LACP works means that > sometimes the data goes across one network port (although I don't understand > why I'm only getting 30mbytes/second per port in that case). > > I'm going to recable things at some point soon, so I'll revisit it after that. > > James >
I also noticed a graph like this once i benchmarked w2k8 guest on ceph with rbd. To me it looked like when the space on the drive is used, the throughput is lower, when the space read by rbd on the drive is unused, the reads are superfast. I don't know how rbd works inside, but i think ceph rbd here returns zeros without real osd disk read if the block/sector of the rbd-disk is unused. That would explain the graph you see. You can try adding a second rbd image and not format/use it and benchmark this disk, then make a filesystem on it and write some data and benchmark again... -- Mit freundlichen Grüßen, Florian Wiessner Smart Weblications GmbH Martinsberger Str. 1 D-95119 Naila fon.: +49 9282 9638 200 fax.: +49 9282 9638 205 24/7: +49 900 144 000 00 - 0,99 EUR/Min* http://www.smart-weblications.de -- Sitz der Gesellschaft: Naila Geschäftsführer: Florian Wiessner HRB-Nr.: HRB 3840 Amtsgericht Hof *aus dem dt. Festnetz, ggf. abweichende Preise aus dem Mobilfunknetz _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
