I was recently introduced to the idea of a parity drive, a specially reserved hard drive in a data server array that can be used to recover data when another drive fails. The clever thing about a parity drive is that no matter how many hard drives are in your array, you only ever need one parity drive to provide fault tolerance for all of them1. How is it possible for one hard drive to recreate data from 10 or even 100 other hard drives?
