Exploiting In-Memory And On-Disk Redundancy To Conserve Energy In Storage Systems

Today\u27s storage system places an imperative demand on energy efficiency. Storage system often places disks into standby mode by stopping them from spinning to conserve energy when load is not high. The major obstacle of this method is by introducing a high spin-up cost introduced by passively waking up the standby disk to service the request. In this paper, we propose a redundancy-based, hierarchical I/O cache architecture called RIMAC to solve the problem. The idea of RIMAC is to enable data on the standby disk(s) to be recovered by accessing two-level I/O cache and/or active disks if needed. In parity-based redundant disk arrays, RIMAC exploits parity redundancy to dynamically XOR-reconstruct data being accessed toward standby disk(s) at both cache and disk levels. By avoiding passive spin-ups, RIMAC can significantly improve both energy efficiency and performance. We evaluated RIMAC by augmenting a validated storage system simulator disksim and tested four real-life server traces including HP\u27s cello99, TPC-D, OLTP and SPC\u27s search engine. Comprehensive results indicate RIMAC is able to reduce energy consumption by up to 18 percent and simultaneously improve the average response time by up to 34 percent in a small-scale RAID-5 system compared with threshold-based power management schemes. © 2008 IEEE