Using MEMS-based storage in disk arrays

Abstract

Current disk arrays, the basic building blocks of high-performance storage systems, are built around two memory technologies: magnetic disk drives, and non-volatile DRAM caches. Disk latencies are higher by six orders of magnitude than non-volatile DRAM access times, but cache costs over 1000 times more per byte. A new storage technology based on microelectromechanical systems (MEMS) will soon offer a new set of performance and cost characteristics that bridge the gap between disk drives and the caches. We evaluate potential gains in performance and cost by incorporating MEMS-based storage in disk arrays. Our evaluation is based on exploring potential placements of MEMS-based storage in a disk array. We used detailed disk array simulators to replay I/O traces of real applications for the evaluation. We show that replacing disks with MEMS-based storage can improve the array performance dramatically, with a cost performance ratio several times better than conventional arrays even if MEMS storage costs ten times as much as disk. We also demonstrate that hybrid MEMS/disk arrays, which cost less than purely MEMS-based arrays, can provide substantial improvements in performance and cost/performance over conventional arrays.