S-RAID 5: An energy-saving RAID for sequential access based applications

In modern-day storage systems, disk arrays and their cooling systems consume a major portion of total system power consumption. The existing research work on energy conservation mainly concentrates on optimizing the storage systems for random access-based applications. However, for the widely-used storage systems for sequential access-based applications, such as video surveillance, continuous data protection (CDP), virtual tape library (VTL), few schemes are proposed to gain better energy conservation according to their inherent characteristics with I/O performance guarantee so far. To this end, S-RAID 5, an energy-saving RAID system, is proposed for sequential access-based applications. In S-RAID 5, a local-parallelism strategy is employed: the entire storage area of the array is partitioned into different groups, and in each group a parallel data access scheme is adopted. Data grouping makes it possible to keep only a portion of disks active while keeping the rest standby. On the other hand, the intra-group parallelism is used to provide the performance guarantee. With an appropriate caching strategy to filter out a small amount of random accesses, S-RAID 5 can achieve prominent energy saving. In a simulation experiment of 32-channel video surveillance with D1 resolution standard, the measurement results of 24-hour power consumption show that the power consumption of S-RAID 5 is 59%, 23%, 21%, and 21% of those of Hibernator, eRAID, PARAID, and GRAID, respectively, while meeting the I/O performance and single-disk fault tolerance.