Hi Florian, On Wed, Jul 25, 2012 at 10:06:04PM +0200, Florian Haas wrote: > Hi Mehdi, > For the OSD tests, which OSD filesystem are you testing on? Are you > using a separate journal device? If yes, what type? Actually, I use xfs and the journal is on a same disk in an other partition. After reading documentation, I seems that using a dedicated disk is better and SSD is a good choice. > seekwatcher -t rbd-latency-write.trace -o rbd-latency-write.png -p 'dd > if=/dev/zero of=/dev/rbd0 bs=4M count=1000 oflag=direct' -d /dev/rbd0 > > Just making sure: are you getting the same numbers just with dd, > rather than dd invoked by seekwatcher? yes > > Also, for your dd latency test of 4M direct I/O reads writes, you seem > to be getting 39 and 300 ms average latency, yet further down it says > "RBD latency read/write: 28ms and 114.5ms". Any explanation for the > write latency being cut in half on what was apparently a different > test run? Yes this is a different run, the one on the bottom was with less servers but with better hardware. > > Also, were read and write caches cleared between tests? (echo 3 > > /proc/sys/vm/drop_caches) No, I will add it > Cheers, > Florian I known that my setup is not really optimal, Writing these tests help me to understand how ceph work and I'm sure with your advice I will build a better cluster :) Thanks for your help. Cheers, -- Mehdi Abaakouk mail: sileht@xxxxxxxxxx irc: sileht
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