We have had far more downtime and lost data due to failed hardware RAID controllers
than to failed disk drives.
Unless you're talkign about a pre-integrated system like a NetApp or can prove that your system is seriously CPU-bound,
use software RAID. The fact that you can plug half your
mirror into any system and have it work is priceless.
OK, all of my experience is with SCSI, I know IDE takes
more CPU, so maybe it makes some sense there. But I don't
think the supposed benefits of hardware RAID outweigh the risk you'll lose everything if the totally proprietary layout of your disks goes haywire.
Yeah, with software RAID you usually lose the ability to
hot-swap a replacement disk. In practive I found that feature useful
and functional ONCE. I've had disks in large software RAID
systems fail 3 or 4 times and have never had problems
scheduling a quick reboot to swap drives. Usually it's time
for a kernel upgrade anyway. The actual RAID rebuild can be
done while the system is running.
