I think what praetor means is what kind of raid array would you like. There is a Raid 0, also known as disk striping, which focuses on performance and speed as your data is ran on both HDD's as one drive (short summarized version), or you could have a Raid 1, also known as disk mirroring, which focuses on one drive as a back up to your other drive of the same capacity and speed (same model usually). So the question is do you want speed and performance or backed up data. There are quite a few other Raid configs but those two are the main ones that beginners and intermediates like me focus on, and I'm assuming that these are what you are looking for too. Find out if you have SATA plug-ins on your mobo and if you'll need to buy a seperate pci card (Only if your HDD's are SATA enabled though). SATA is slightly faster than the classic IDE setup. Hope this was helpful...