I've built my own computers but never had to deal with SCSI. But for my next project I plan on slotting 4 HDs in a raid config, probably raid 5. From doing research on it, I've noticed that the word (or anacronym actually) SCSI flying around. Is it a PCI slot card that you plug the HDs into? Or is it something external? I tried to look it up online but what I was reading didn't really answer any questions.