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Performance study of RAID-5 disk arrays with data and parity cache

Disk array architectures such as RAID-5 have become an acceptable way far designing highly reliable and high-performance storage systems. However one major drawback of a RAID-5 disk array system is that an update to a data block may involve four disk accesses. Such a high overhead is especially undesirable for workloads with high update rate as in transaction processing. In this paper, we present a new scheme for improving the write performance of disk arrays using controller cache to store data as well as parity information. We have developed a trace-driven model to simulate cached disk arrays for transaction processing environment. We have studied the effect of caching parity information at the controller level along with caching data. The simulation results show a considerable improvement in response time of data and parity cached disk array over disk arrays with only data caching. The improvement in response time for disk array employing parity cache is about 10%-20% for the parameters used in our study.