DCS5: Diagonal Coding Scheme for Enhancing the Endurance of SSD-Based RAID-5 Systems

Abstract

Solid-state drives (SSDs) have been widely deployed in large-scale storage systems. To guarantee high reliability for SSD-based storage systems, it still requires data redundancy schemes, e.g., RAID schemes. Traditional RAID-5 shows its benefits in load-balancing and I/O parallelism, and so it is still the first choice for enhancing the reliability of SSD RAID arrays. However, some SSDs under the RAID-5 configuration may age much faster than others because of the non-uniformity of workloads, which makes them be worn out very quickly and so decreases the endurance of SSD-based RAID arrays. To address this problem, we develop a diagonal coding scheme, DCS5, to improve the wear-leveling among devices in an SSD-based RAID-5 array. DCS5 can efficiently improve the array endurance if accesses are aligned with the stripe size, i.e., When data symbols in the same stripe receive the same number of writes, while the number could be different for different stripes. To relax the above assumption, we further propose an enhanced scheme which is called as DCS5+. DCS5+ can improve the wear-leveling among devices under general access patterns via triggering different responses to different kinds of requests. We conduct extensive trace-driven evaluations based on real-world workloads, and results show that our coding scheme efficiently enhances the endurance of SSD-based RAID-5 arrays.