On Tue, Dec 9, 2008 at 5:17 AM, Mario Weilguni <mweilguni@xxxxxxxx> wrote: > Alan Hodgson schrieb: >>>>>> >>>>>> Mario Weilguni <mweilguni@xxxxxxxx> wrote: >>>>>> >>>> >>>> strange values. An individual drive is capable of delivering 91 >>>> MB/sec >>>> sequential read performance, and we get values ~102MB/sec out of a >>>> 8-drive RAID5, seems to be ridiculous slow. >> >> >> What command are you using to test the reads? >> >> Some recommendations to try: >> >> 1) /sbin/blockdev --setra 2048 device (where device is the partition or >> LVM volume) >> >> 2) Use XFS, and make sure your stripe settings match the RAID. >> >> Having said that, 102MB/sec sounds really low for any modern controller >> with 8 drives, regardless of tuning or filesystem choice. >> >> > > First, thanks alot for this and all the other answers. > > I measured the raw device performance: > dd if=/dev/cciss/c0d0 bs=64k count=100000 of=/dev/null > > I get poor performance when all 8 drives are configured as one, large > RAID-5, and slightly poorer performance when configured as JBOD. In > production, we use XFS as FS, but I doubt this has anything to do with FS > tuning. Yeah, having just trawled the pgsql-performance archives, there are plenty of instances of people having terrible performance from HP smart array controllers before the P800. Is it possible for you to trade up to a better RAID controller? Whichever salesman sold you the P400 should take one for the team and make this right for you. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
