http://en.wikipedia.org/wiki/Redunda...ependent_disks

With RAID 0 you combine two or more hard drives to increase the speed data transfer. The only bad thing is that if a hard drive fails, you lose all your data on both drives.

If you wanted an fast and easy to understand solution I guess you could go with a Solid State hard drive for your WoW folder. It'd be faster than a RAID, and (potentially) less trouble.