The performance of parity placements in disk arrays

Due to recent advances in central processing unit (CPU) and memory system performance, input/output (I/O) systems are increasingly limiting the performance of modern computer systems. Redundant arrays of inexpensive disks (RAID) have been proposed to meet the impending I/O crisis. RAIDs substitute many small inexpensive disks for a few large expensive disks to provide higher performance, smaller footprints, and lower power consumption at a lower cost than the large expensive disks they replace. RAIDs provide high availability by using parity encoding of data to survive disk failures. It is shown that the way parity is distributed in a RAID has significant consequences for performance. The performances of eight different parity placements are investigated using simulation