UNIFORM PARITY GROUP DISTRIBUTION IN DISK ARRAYS WITH MULTIPLE FAILURES

Several new disk arrays have recently been proposed in which the parit y 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 perf ormance. Many arrays now also put in multiple spare disks so that expe nsive service calls can be deferred. Furthermore, in a new sparing sch eme called distributed sparing, the spare spaces are actually distribu ted throughout the array. This means after a rebuild the new array wil l be logically different from the original array. This brief contribut ion presents an algorithm for constructing and maintaining arrays with distributed sparing so that repeated uniform parity group distributio n is achieved with each successive failure.