As a followup, I'd like to point out that you can probably get more
performance wise from hardware upgrades than from tuning your OS.
Something as simple as an $800 caching RAID controller can make a
workstation class machine into a monster performer, going from 250 tps
to 3000 tps with one simple change. Tuning might get you from 250 to
275. Hardware upgrades can take you much much further. Memory
upgrades are cheap (I just ordered 8 Gigs for my laptop for $89). 4G
ECC RAM is pretty cheap for servers too. Any newly minted database
server with less than 16 gigs of ram is inexcusable today. 32 is
really the minimum I'd throw at a new server now. Also, very fast 8
or 12 core cpus, both from intel and amd, are cheap too. An 8 core
2.0GHz Magny Cours on newegg is only $275. Put a pair of those in a
db server with 32 Gigs ram and a decent caching RAID controller and a
handful of decent hard drives and you don't really need to do a lot of
tuning. Even a 4 drive machine can give a good account of itself with
that hardware.
What I'm trying to say is don't spend tons of time tuning slow
hardware, you'll get at most a few % gain.