A SystemTap update

Actually the block_dump feature of modern 2.6 linux kernels will show you which processes are writing to which devices. I wrote a proof of concept script to show them:

http://www.digitalprognosis.com/opensource/scripts/top-di...

The output looks like this:
root@desktopmonster:~# ./top-disk-users
COMMAND PID NUM ACTION DEVICE
banshee-1 23999 8 READ sda9
kjournald 2494 131 WRITE sda5
kjournald 5182 5 WRITE sda8
pdflush 228 15 WRITE sda5
pdflush 228 1 WRITE sda8
pdflush 228 32 WRITE sda9