${\rm S}^{2}$ -RAID: Parallel RAID Architecture for Fast Data Recovery

As disk volume grows rapidly with terabyte disk becoming a norm, RAID reconstruction process in case of a failure takes prohibitively long time. This paper presents a new RAID architecture, S²-RAID, allowing the disk array to reconstruct very quickly in case of a disk failure. The idea is to form skewed sub-arrays in the RAID structure so that reconstruction can be done in parallel dramatically speeding up data reconstruction process and hence minimizing the chance of data loss. We analyse the data recovery ability of this architecture and show its good scalability. A prototype S²-RAID system has been built and implemented in the Linux operating system for the purpose of evaluating its performance potential. Real world I/O traces including SPC, Microsoft, and a collection of a production environment have been used to measure the performance of S²-RAID as compared to existing baseline software RAID5, Parity Declustering, and RAID50. Experimental results show that our new S²-RAID speeds up data reconstruction time by a factor 2 to 4 compared to the traditional RAID. Meanwhile, S²-RAID keeps comparable production performance to that of the baseline RAID layouts while online RAID reconstruction is in progress.