Ps-code: A new code for improved degraded mode read and write performance of RAID systems

The newer storage systems often have to deal with multiple disk failures. Thus, RAID (Redundant Array of Independent Disk) is becoming increasingly important for two primary benefits: (1) high read performance and (2) robust fault tolerance. In addition, the recent RAID codes achieve better IO performance by using only XORs (optimal computational complexity) to compute parities. However, this achieved optimal computational complexity limits the further IO performance improvement. In this paper, we are proposing a new code called PS-code (Parity Stripe code) that employs improved Cauchy Reed Solomon codes for computing the parity to further improve write and degraded mode read performance. Furthermore, we extend the novelty by reducing the number of writes required for updating the parity. We simulated the PS-code in the DiskSim environment and devised a new metric called multi- block access complexity to perform an improved evaluation of the performance of the PS-code on workloads that represent real life scenario such as multi-block updates. Also, the experimental results demonstrate that the PS-code, on average, achieves 66%-86% better write performance and achieves 8.9%-23.6% higher degraded-mode read performance compared to previous works including P-code, RDP code, X-code, and HV-code. Finally, the comparison between the vertical and horizontal codes demonstrates that the vertical codes have better read performance than the horizontal codes in most cases.