Trade-offs between devices and paths in achieving disk interleaving

Four alternative implementations for achieving higher data rates in a disk subsystem (parallel heads without replication, parallel heads with replication, parallel actuators without replication, and parallel actuators with replication) are studied. Focus is on the tradeoffs between the number of devices and the number of data paths while keeping the number of physical devices constant (which may keep the cost roughly constant). The performance advantages and limitations of the alternative implementations are analyzed using an analytic queuing model and compared to a conventional disk subsystem. The study shows that parallel heads with replication from a single actuator performs the best for the average application environments, although other configurations may be more cost-effective