Logging Raid - An Approach to Fast, Reliable, and Low-Cost Disk Arrays

The parity-based disk arrays provide high reliability and high performance for read and large write accesses at low storage hardware cost. However, small writes are notoriously slow, since each small write typically incurs 4 I/O operations due to the parity update. This paper presents logging RAID, a disk array architecture that adopts logging techniques to cure the small-write problem in parity-based disk arrays. Logging RAID achieves high performance for a wide variety of I/O access patterns. We present a set of trace-driven simulation results, and show that logging RAID can achieve excellent performance levels with very small storage space overhead. We also compare logging RAID with two closely related schemes, AutoRAID and log-Structured Array (LSA), and point out the distinguishing features of logging RAID and the performance advantages that logging RAID enjoys.