Uniform parity group distribution in disk arrays with multiple failures

Several new disk arrays have recently been proposed in which the parity groupings are uniformly distributed throughout the array so that the extra workload created by a disk failure can be evenly shared by all the surviving disks, resulting in the best possible degraded mode performance. Many arrays now also put in multiple spare disks so that expensive service calls can be deferred. Furthermore, in a new sparing scheme called distributed sparing, the spare spaces are actually distributed throughout the array. This means after a rebuild the new array will be logically different from the original array. The authors present an algorithm for constructing and maintaining arrays with distributed sparing so that repeated uniform parity group distribution is achieved with each successive failure