My RAID 1 controller is a Promise something-something 2000. I installed two (formatted) HD's and booted up. The controller's bios detected the drives and asked a couple of questions regarding what I wanted to do (raid 0? raid 1? raid 10?) and then set it up. Only took a minute or so.

It's running on a 1.8 GHz machine w/XP pro and just sits on the cat 5 cable in the basement. The array is mapped so that each computer has its own pot to dump stuff into. If I remote (or physically) access the computer I can see all the folders, but in general each user has his/her own space to store things.

At any rate, the drives had to be formatted, and the controller just arranged its' internal logic to do what I wanted. No additional formatting (of the drive) required.