The CPU load is negligible. Reading performance is about 20% better. Best regards and my apologies for my bad English. GTP.S.: on a P800, 12 SATA 750GB 3,5" 7200 rpm, the hardware raid5 writing performance was about 30 MB/s, software raid5 is between 60 and 80 MB/s.
Scott Marlowe ha scritto:
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.
Attachment:
smime.p7s
Description: S/MIME Cryptographic Signature
