well the RAID allows you more abilities then standard IDE. You can use a couple of drives to make a stripped set for speed, or do mirroring for backup/fault tolerance. The RAID is only another layer to the system. No different then going out and getting a RAID controller and then running drives from that, only this is on your board. Depending on the controller used, you will have several choices. RAID1 and 0 being the most common. Raid0 is stripping, RAID1 is mirrored. JBOD(not sure if that is correct or not) is a spanning setup. It allows you to span the size of the drives out without any speed increase or fault tolerance. Mirrored drives are nice for system drives, cause if one dies, then you can switch to the other right away.
Stripped is great if you do video or a lot of data crunching cause you get a speed increase of almost 2x. if you do RAID with you system there are several things to keep in mind...
With stripping, you want to use alternate channels for the drives. Otherwise, you get all the data on one channel of the controller and loose the speed increase. If you stripe out two sets of drives, cross them over the channels. Like use the masters on IDERAID 1 and 0 then use the slaves on IDERAID 1 and 0. That will keep the speed up without causeing trouble.
You may also have the option to do RAID0+1 which is mirroring a stripped set. Takes 4 drives, but can be worth it...
Finally, unless you have two drives of the same size, don't stripe them. The stripe set will take the smaller drive size and only allow you to use that size to both drives reguardless of the actuall capacity. And you need TWO drives to use raid, unless you have JBOD available...
Oh, one other thing, then you install the OS, if it's windows, you have to feed it the RAID driver during install or it will not see the drives there...
Good luck.
