On Aug 17, 2011, at 4:17 PM, Greg Smith wrote: > On 08/17/2011 02:26 PM, Ogden wrote: >> I am using bonnie++ to benchmark our current Postgres system (on RAID 5) >> with the new one we have, which I have configured with RAID 10. The drives >> are the same (SAS 15K). I tried the new system with ext3 and then XFS but >> the results seem really outrageous as compared to the current system, or am >> I reading things wrong? >> >> The benchmark results are here: >> http://malekkoheavyindustry.com/benchmark.html > > Congratulations--you're now qualified to be a member of the "RAID5 sucks" > club. You can find other members at > http://www.miracleas.com/BAARF/BAARF2.html Reasonable read speeds and just > terrible write ones are expected if that's on your old hardware. Your new > results are what I would expect from the hardware you've described. > > The only thing that looks weird are your ext4 "Sequential Output - Block" > results. They should be between the ext3 and the XFS results, not far lower > than either. Normally this only comes from using a bad set of mount options. > With a battery-backed write cache, you'd want to use "nobarrier" for > example; if you didn't do that, that can crush output rates.
I have mounted the ext4 system with the nobarrier option: /dev/sdb1 on /var/lib/pgsql type ext4 (rw,noatime,data=writeback,barrier=0,nobh,errors=remount-ro) Yet the results show absolutely a decrease in performance in the ext4 "Sequential Output - Block" results: http://malekkoheavyindustry.com/benchmark.html However, the Random seeks is better, even more so than XFS... Any thoughts as to why this is occurring? Ogden
