Linux Magazine published an introduction to RAID
One of the most common techniques to improve either data reliability or data performance (or both) is called RAID (Redundant Array of Inexpensive Disks). The concept was developed in 1977 by David Patterson, Garth Gibson, and Randy Katz as a way to use several inexpensive disks to create a single disk from the perspective of the OS while also achieving enhanced reliability or performance or both.Introduction to RAID