I'm confused, are you talking about an onboard RAID controller, a PCI controller, and what controller exactly is it?
RAID-0 is generally called "striped array", where the data is split between 2 or more drives. It's not as reliable as other methods, but is faster. how fast depends on the drives you use. Creating an array with existing drives will wipe all the data on them. you need 2 identical drives for RAID-0. there are a couple good manuals and FAQ's available at www.promise.com