Abstract
In modern energy-saving replication storage systems, a primarygroup of disks is always powered up to serve incoming requests whileother disks are often spun down to save energy during slack periods.However, since new writes cannot be immediately synchronized intoall disks, system reliability is degraded. In this paper, we developa high-reliability and energy-efficient replication storage system,named RERAID, based on RAID10. RERAID employs part of the free spacein the primary disk group and uses erasure coding to construct a codecache at the front end to absorb new writes. Since code cache supportsfailure recovery of two or more disks by using erasure coding, RERAIDguarantees a reliability comparable with that of the RAID10 storagesystem. In addition, we develop an algorithm, called erasure codingwrite (ECW), to buffer many small random writes into a few large writes,which are then written to the code cache in a parallel fashion sequentiallyto improve the write performance. Experimental results show that RERAIDsignificantly improves write performance and saves more energy thanexisting solutions.