Power management of MEMS-based storage devices for mobile systems

Because of its small form factor, high capacity, and expected low cost, MEMS-based storage is a suitable storage technology for mobile systems. MEMS-based storage devices should also be energy efficient for deployment in mobile systems. The problem is that MEMS-based storage devices are mechanical, and thus consume a large amount of energy when idle. Therefore, a power management (PM) policy is needed that maximizes energy saving while minimizing performance degradation. In this work, we quantitatively demonstrate the optimality of the fixed-timeout PM policy for MEMS-based storage devices. Because the media sled is suspended by springs across the head array in MEMS-based storage devices, we show that these devices (1) lack mechanical startup overhead and (2) exhibit small shutdown overhead. As a result, we show that the combination of a PM policy, that fixes the timeout in the range of 1--10 ms, and a shutdown policy, that exploits the springs, results in a near-optimal energy saving yet at a negligible loss in performance.