I only use SSDs, which is why I’m so surprised at the CFQ behaviour - the drive can sustain tens of thousand of reads per second, thousands of writes - yet saturating it with reads drops the writes to 10 IOPS - that’s mind boggling to me. Jan > On 23 Jun 2015, at 13:43, Dan van der Ster <dan@xxxxxxxxxxxxxx> wrote: > > On Tue, Jun 23, 2015 at 1:37 PM, Jan Schermer <jan@xxxxxxxxxxx> wrote: >> Yes, I use the same drive >> >> one partition for journal >> other for xfs with filestore >> >> I am seeing slow requests when backfills are occuring - backfills hit the filestore but slow requests are (most probably) writes going to the journal - 10 IOPS is just to few for anything. >> >> >> My Ceph version is dumpling - that explains the integers. >> So it’s possible it doesn’t work at all? > > I thought that bug was fixed. You can check if it worked by using > "iotop -b -n1" and looking for threads with the idle priority. > >> Bad news about the backfills no being in the disk thread, I might have to use deadline after all. > > If your experience follows the same paths of most users, eventually > deep scrubs will cause latency issues and you'll switch back to cfq > plus ionicing the disk thread. > > Are you using Ceph RBD or object storage? If RBD, eventually you'll > find that you need to put the journals on an SSD. > > Cheers, Dan _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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