On Tuesday, May 22, 2012 at 1:30 PM, Stefan Priebe wrote: > Am 22.05.2012 21:52, schrieb Greg Farnum: > > On Tuesday, May 22, 2012 at 12:40 PM, Stefan Priebe wrote: > > Huh. That's less than I would expect. Especially since it ought to be going through the page cache. > > What version of RBD is KVM using here? > > > v0.47.1 > > > Can you (from the KVM host) run > > "rados -p data bench seq 60 -t 1" > > "rados -p data bench seq 60 -t 16" > > and paste the final output from both? > > > OK here it is first with write then with seq read. > > # rados -p data bench 60 write -t 1 > # rados -p data bench 60 write -t 16 > # rados -p data bench 60 seq -t 1 > # rados -p data bench 60 seq -t 16 > > Output is here: > http://pastebin.com/iFy8GS7i Heh, yep, sorry about the commands — haven't run them personally in a while. :) Anyway, it looks like you're just paying a synchronous write penalty, since with 1 write at a time you're getting 30-40MB/s out of rados bench, but with 16 you're getting >100MB/s. (If you bump up past 16 or increase the size of each with -b you may find yourself getting even more.) So try enabling RBD writeback caching — see http://marc.info/?l=ceph-devel&m=133758599712768&w=2 -Greg -- 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
