Large writes making desktop unusable

[snarkout]

I posted this over on the arch fora, but figured I'd ask you folks, too.

I'm trying to figure out the best solution to my current problem - my 3ware raid-5 set sucks. Doing even moderate writes to it absolutely kills my desktop. For example, scping an iso from one box to this box = go make a sammich. I've uptaed the firmware, and have done the things I've had 3ware recommend short of switching this disk to xfs - right now it's ext3. But they insisted that my issues would go away once I got the card into a pci-x slot (it was in a regular pci slot so it made sense) - no dice. I upgraded from an athlon 3200+ to a pentium D 955 and a supermicro mobo, and writes are still *just* as damaging to system performance. Following all of 3wares advices *did* speed things up, but I'd be more happy with twice as slow and still usable. I've read this

http://bbs.archlinux.org/viewtopic.php?t=12865

but as far as I can tell, this is mostly useful for speeding up reads, not writes. I've also tried both the ck kernel and the beyond kernel, and neither of them seem to help much in this case.

Ideas I've had are to just buy another drive, somehow migrate my current install over to it, and keep my raid set as a storage volume. I don't care much about moving files *quickly* from machine to machine, but I do want to be able to do it w/o having to ignore my computer for 10 min (or longer for multi-gig files).

Also, any good plans for migrating an existing install from a raid set to a single drive? Most of the stuff I've read is either absurdly difficult or requires dd, and I'm fairly sure I can't dd 300+ raided gigs onto an 80 or 120 gig drive.

Ideas or suggestions?