Check out this article at Hardware Secrets. Hard Drives are usually the main bottleneck in a computer system and utilizing RAID arrays are a great way to improve disk I/O performance.
Gabriel Torres wrote:RAID (Redundant Array of Independent Disks) systems are used to increase the performance and/or reliability of the hard disk drives of the system. In this article we will explain the basics about RAID0, RAID1, RAID5 and the advantages of RAID6 over them.
http://www.hardwaresecrets.com/article/314