On Fri, 5 Dec 2008, Alan Hodgson wrote:
1) /sbin/blockdev --setra 2048 device (where device is the partition or LVM volume)
Normally, when I see write speed dramatically faster than write, it does mean that something about the read-ahead is set wrong. While I don't have one to check, it looks to me like the P400 does its own read-ahead though, which may be more effective to tweak than what Linux does. I'd suggest taking a look at the settings with HP's admin utility and see how it's set for that and for allocation of RAM to the read cache. I've seen some RAID5 configs that put too much caching on the write side by default to compensate for the deficiencies of that RAID level, and you have to push some of that back toward the read side to balance it out right.
2) Use XFS, and make sure your stripe settings match the RAID.
XFS has good performance, but I can't get over how many system failure corruption reports I hear about it. In any case, there's no reason this system shouldn't perform fine on ext3.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
