Dynamic parity stripe reorganizations for RAID5 disk arrays

RAID5 disk arrays provide high performance and high reliability for reasonable cost. However RAIDS suffers a performance penalty during block updates. We examine the feasibility of using “dynamic parity striping” to improve the performance of block updates. Instead of updating each block independently, this method buffers a number of updates, generates a new stripe composed of the newly updated blocks, then writes the full stripe back to disk. Two implementations are considered in this paper. One is a log-structured file system (LFS) based method and the other is Virtual Striping. Both methods achieve much higher performance than conventional approaches. The performance characteristics of the LFS based method and the Virtual Striping method are clarified