On Tue, Oct 02, 2007 at 09:39:09AM -0400, Ross S. W. Walker wrote: > Simon Banton wrote: > > > > At 12:30 +0200 2/10/07, matthias platzer wrote: > > > > > >What I did to work around them was basically switching to XFS for > > >everything except / (3ware say their cards are fast, but only on > > >XFS) AND using very low nr_requests for every blockdev on the 3ware > > >card. > > > > Hi Matthias, > > > > Thanks for this. In my CentOS 5 tests the nr_requests turned out by > > default to be 128, rather than the 8192 of CentOS 4.5. I'll have a go > > at reducing it still further. > > Yes, the nr_requests should be a realistic reflection of what the > card itself can handle. If too high you will see io_waits stack up > high. > > 64 or 128 are good numbers, rarely have I seen a card that can handle > a depth larger then 128 (some older scsi cards did 256 I think). > Hmm.. let's say you have a linux software md-raid array made of sata drives.. what kind of nr_request values you should use for that for optimal performance? Thanks! -- Pasi