@FEAR The OS has no idea that the 'disk' it sees is on a controller or not. As long as your OS can see the 'drive' you can encapsulate it. So there is no requirement to have the same controller, though with multiple different vendor controllers you'll probably have different performance profiles and you will be taking up more driver space (driver per controller). Now, there may be limitations on booting a 'striped' OS drive I've never tried that but didn't see anything against it. I have not tried it in vista (don't run it) but would be surprised if they removed that feature that was there in xp pro.

@nfo, yes basically you're striping at the OS level but you're doing the raid at the hardware level.