EERAID: energy efficient redundant and inexpensive disk array

Recent research works have been presented on conserving energy for multi-disk systems either at a single disk drive level or at a storage system level and thereby having certain limitations. This paper studies several new redundancy-based, power-aware, I/O request scheduling and cache management policies at the RAID controller level to build energy-efficient RAID systems, by exploiting the redundant information and destage issues of the array for two popular RAID levels, RAID 1 and RAID 5. For RAID 1, we develop a Windowed Round Robin (WRR) request scheduling policy; for RAID 5, we introduce a N-chance Power Aware cache replacement algorithm (NPA) for writes and a Power-Directed, Transformable (PDT) request scheduling policy for reads. Trace-driven simulation proves EERAID saves much more energy than legacy RAIDs and existing solutions.