SPD-RAID4: Splitting Parity Disk for RAID4 Structured Parallel SSD Arrays

Data-intensive applications like video processing and bioinformatics increasingly demand a high-performance and highly reliable storage system. Hard disk drive (HDD) has long been used as a standard storage device for most existing storage systems. Recently, NAND-flash memory based solid state drives (SSDs) are gradually exploited to replace HDDs in enterprise computing infrastructures due to their salient features such as high performance, low power consumption, and excellent shock-resistance. With rapid price decreasing and capacity increasing, flash SSD based disk arrays organized in some RAID structures become feasible and greatly needed. In this paper, we propose a new RAID4 architecture called SPD-RAID4 (Splitting Parity Disk - RAID4) for parallel SSD arrays. It splits the parity disk of a traditional RAID 4 array into configurable number of smaller ones. Thus, multiple small parity SSDs operate in tandem with data SSDs to achieve a high performance and high level of reliability. We compare the performance of SPD-RAID4 with conventional RAID4 and RAID5 architectures by using both real-world traces and synthetic benchmarks. Experimental results demonstrate that in terms of mean response time SPD-RAID4 outperforms standard RAID5 structured SSD arrays by up to 20.3%. Compared with standard RAID4, SPD-RAID4 achieves a performance gain up to 40.6%.