Aaron,
For Raid5 you need at least 3 HDs
SME supports (Software) Raid directly from the kernel.
Support software incl. mdadm is part of the base-package.
Raid1 is even in the SME auto-setup.
Raid5 can be easily done ... just use the search button here... (incl. show all ...)
A hardware Raid controller has to be supported in the kernel or via (working!!!) driver (look for RH 6.3 hardware compatibility list).
3ware is the champion here...
With Highpoint, Promise and Silicon Magic "Raid"-controllers you'll be mostly on your own - or worse "out of luck".
This is a topic that is discussed once a week so you will find plenty in this forum.
Regards
Reinhold