TeraTeam UK Teradata DBA Definition
term: XOR
An "exclusive-or" (XOR) algorithm, sometimes called "binary math," is used to write data to RAID 5 (in EMC drives, RAID S) disk arrays. With binary math, the only values allowed are 0 and 1. To calculate the parity bytes, the disk array controllers add the various combinations of 1 and 0 to calculate a missing byte:
- An even number of 1's calculates to a 0. For example: 1 + 1 = 0
- An odd number of 1's calculates to a 1. For example: 1 + 1 + 1 = 1
