Using non-volatile storage to improve the reliability of RAID5 disk arrays

RAID5 disk arrays are becoming popular solutions for providing fast access to data for transaction processing applications. They provide good performance at low cost without sacrificing much data reliability. Their main drawback is poor performance for small write requests. Techniques for using non-volatile RAM (NVRAM) have been proposed for improving the performance of these write requests. The paper shows that NVRAM and other nonvolatile devices can also be used to improve the reliability of an array by significantly reducing the time required to repair a failed disk: in the array in the event of a single disk failure. More importantly, proper use of these non-volatile devices allows the array to support heavier workloads than previously reported yet still repair a failed disk in a reasonable amount of time.