depends on what you are trying to accomplish:
deal is that raid needs to be done right, first of all you need a raid card, and not the one built into your mobo, because that is not a true raid card, i mean a pci-ex raid card, they are a bit on the expensive side. That's when raid gets performance, or reliability boost.
It's not complicated to set up, you would go into raid card firmware and create a raided drive, at that point your computer will see one drive, instead of 2 hard drives, what level you use depends on what you try to accomplish: (i swear i have written about this before)
RAID stands for Redundant Array of Inexpensive Disks, but it can be more then just that
raid 0 - data is written across the disks in stripes, alowing for 2 simultaneous write operations to both disks. This greatly increases the speed, but as i said, really noticeable with a real hardware controller
raid 1 - what is written to one drive, is written to the other, this decreases your total space to one drive, but it provides redundancy, if one drive fails, the data is still on the other one
raid 5 - need at least 3 drives for this, but this allows for one drive to fail, the data exists on the other ones still (you can opt to have a hot spare here too)
raid 10 - need at least 4 drives, combination of 2 raid 1 arrays in raid 0, providing both speed of raid 0, and redundancy of raid 1 (you loose 2 drives in translation)
those are your most basic and commonly used ones, though you wont generally see 5 or 10 on machines, i can't say that i haven't....
raid is not really a need, it more of a, what you wanna do, thing
