It is also a perfectly normal thing to have more than 1 drive. Why do you think a motherboard has the capability of hooking up 4, 6 even 8 or more drives? Gives you room to store more stuff, a second place to keep all you important data in case 1 drive fails, run RAID arrays, or simply organize lots and lots of data, like movies for instance. And yes, there can be performance advantages in certain applications.