Rod: a Practical Approach to Improving Reliability of Energy-efficient Parallel Disk Systems

The Massive Array of Idle Disks (MAID) technique is an effective energy saving schemes for parallel disk systems. The goal MAID is to skew I/O load towards a few disks so that other disks can be transitioned to low power states to conserve energy. I/O load skewing techniques like MAID inherently affect reliability of parallel disks because disks storing popular data tend to have high failure rates than disks storing cold data. To achieve good tradeoffs between energy efficiency and disk reliability, we first present a reliability model to quantitatively study the reliability of energy-efficient parallel disk systems equipped with MAID schemes. Then, we propose a novel strategy— disk swapping—to improve disk reliability by alternating disks storing hot data with disks holding cold data. At Last, we further improve disk reliability by introducing multiple disk swapping strategy. We demonstrate that our disk-swapping strategies not only can increase the lifetime of cache disks in MAID-based parallel disk systems, but also further reduce the failure rate of the entire system when the multiple-disk swapping is introduced.