I haven't been able to find a good answer, so I figure if I can find someone who has a raid setup maybe this person could help.
I've recently thought about setting up a raid with two extra drives so I can mirror them both, and have a good back up system. My motherboard supports it, however I found an external drive bay that'll run the raid I want over USB2.0 or serial ata. The only reason I'm considering the external one is if say down the road I have to get a new motherboard, is it a pain to put the new drives on the mother board and get a raid going again without losing data? That is my only concern that it seems I wouldn't have with the external setup. I just plug it in like an external drive.
If setting it up on the motherboard isn't a big deal, and if taking two drives that are mirrored and setting them up on a new motherboard later isn't either, I would go with that.
My motherboard is asus if that helps, however I don't know if it would.