Kjell,
> I got 4 150GIG SCSI disks in a Smart Array 5i 1+0 RAID.
The Smart Array 5i is a terrible performer on Linux. I would be
surprised if you exceed the performance of a single hard drive with this
controller when doing I/O from disk. Since your database working set is
larger than memory on the machine, I would recommend you use a simple
non-RAID U320 SCSI controller, like those from LSI Logic (which HP
resells) and implement Linux software RAID. You should see a nearly 10x
increase in performance as compared to the SmartArray 5i.
If you have a good relationship with HP, please ask them for some
documentation of RAID performance on Linux with the SmartArray 5i. I
predict they will tell you what they've told me and others: "the 5i is
only useful for booting the OS". Alternately they could say: "we have
world record performance with our RAID controllers", in which case you
should ask them if that was with the 5i on Linux or whether it was the
6-series on Windows.
- Luke