Harddrive duplication.


In Runtime
I have 4 western digital 80 gig 7200 rpm SATA drives hooked-up in a raid mirrored 0+1 array, with a 10,000 rpm raptor acting as some kind of governing drive. (Please note that this system was set-up FOR me, not BY me, thus the lack of knowledge.)

Recently, when I turn on the system, it will go to some kind of bios like thing, and say that it want's to duplicate hardrives to ensure stability or something. I didn't to duplicate, as I didn't know what that would do, so I chose not to duplicate. System booted fine and seems to be fully operational. This does this every time I boot up now though, so I am getting worried about shutting my comp off. What does this mean...is one of my hardrives failing? Any and ally help/info will be much appreciated. Thanks.