.. taking extra care to read
http://en.wikipedia.org/wiki/RAID_5#RAID_5_disk_failure_rate
If you don't fully understand that section, you do not want to run RAID-5.
If you DO understand that section, you still don't want to run RAID-5 (

) but you can do so at your own risk.
Personally, I think using RAID for volume management is evil.
Read up a bit on ZFS (I'd give you the details, but TS would have me assassinated

), and wait for Snow Leopard if you can.
Let me summarize:
RAID is not a backup system.
The vast majority of non-business users should probably avoid RAID altogether. RAID is not a backup system. RAID (Except RAID 0) provides redundancy for high availability. Most non-business users would be better off spending their money and efforts on a backup system.
RAID is not a backup system.
If you are going to use OS-independent RAID, then RAID 1 or RAID 1+0 are the best choices.
RAID 0 (striping) is a very poor choice unless you need, and I mean really
need, the extra speed. If you use RAID 0, it is critical that you backup your data on a regular basis. I'd recommend nightly.
RAID 5/6 is not the panacea many think it is. In fact, it has several major flaws that make it a bad choice because of the RAID 5/6 write hole. There are other performance and array rebuild issues that make RAID 5/6 a bad choice.
RAID 1 is a simple mirror and is a good way to increase availability.
RAID 1+0 offers mirroring and striping so you get some speed advantages along with the higher availability offered by mirroring.
RAID is not a backup system.
ZFS and RAID Z (Z, Z1, Z2) are great because ZFS is self healing and RAID Z1/Z2 don't have the write hole issue. There are plenty of great reasons to go ZFS and RAID Z. RAID Z is software-based and seems to perform as well as dedicated hardware RAID. But, we have to wait until we get ZFS on Mac workstations....
Did I say that RAID is not a backup system yet?
S-