Dynamic Parity Grouping for Improving Write Performance of RAID-5 Disk Arrays

One major drawback of a RAIDS 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 a high update rate. In this paper, we present a dynamic parity grouping (DPG) scheme for efficient parity buffering to reduce the write overhead of a RAID-5 system. In DPG, special parity groups are dynamically created for data blocks with high write activity, referred to as the hot data blocks, in addition to default parity groups for the remaining cold data blocks. The parity blocks of the special parity groups are then buffered in the disk controller cache. As a result, the number of disk accesses on a write to a hot data block is reduced to two.