R&D: Asymmetric RAID, Rethinking RAID for SSD Heterogeneity

ACM Digital Library has published, in HotStorage ’24: Proceedings of the 16th ACM Workshop on Hot Topics in Storage and File Systems, an article written by Ziyang Jiao, and Bryan S. Kim, Syracuse University, Syracuse, New York, USA.

Abstract: “Traditional RAID solutions (e.g., Linux MD) balance writes evenly across the array for high I/O parallelism and data reliability. This is built around the assumption that the underlying storage components are homogeneous, both in performance and capacity. However, SSDs, even for the same model, exhibit very different characteristics and degrade over time, leading to severe disk under-utilization.“

“In this work, we present Asymmetric-RAID (Asym-RAID), a novel RAID architecture that optimizes system performance and storage utilization by exploiting heterogeneity from a larger SSD pool. Asym-RAID asymmetrically distributes data across the array to fully utilize the capacity of each SSD. To improve performance, Asym-RAID differentially exports the address space of each data stripe to the host, allowing for performance-optimized data placement. We outline the necessary changes in the storage stack for building an asymmetric RAID system and highlight its benefits.“