Crosshatch disk arrays for improved reliability and performance

Abstract

Redundant disk array architecture provides fault tolerance against disk drive failures. However, a storage subsystem consists of more than just disk drives. There must also be controllers for interfacing with the disk drives, cabling for providing data/control paths, power supplies, etc. For the subsystem to be fault tolerant, it must also be able to tolerate failure in any one of these components. While currently known array architectures can be designed to be tolerant to single failure in the support hardware, little attention has been paid to performance in the event of such failures. The recovery procedures required after such failures have been repaired were also not fully considered. In this paper a new array architecture is presented which outperforms other currently known array architectures when some supporting hardware such as a controller or cable has failed. Furthermore, this architecture is fault tolerant to at least double failures in the support hardware and is, therefore, a more reliable and robust architecture.