R&D: Maximizing Peformance/Cost Figure of Merit of Storage-Type SCM-Based SSD by Adding Small Capacity of Memory-Type SCM

IEEE Xplore has published, in 2018 Non-Volatile Memory Technology Symposium (NVMTS), an article written by Reika Kinoshita, Department of Electrical, Electronic and Communication Engineering, Chihiro Matsui, Research and Development Initiative, Chuo University, Tokyo, Japan, Shinpei Matsuda,Yutaka Adachi, and Ken Takeuchi, Department of Electrical, Electronic and Communication Engineering, Faculty of Science and Engineering, Chuo University, Tokyo, Japan.

Abstract: “Non-volatile memories called ‘storage class memories (SCMs)’ attract attentions to realize high-performance solidstate drive (SSD). Although storage-type SCM (S-SCM) based SSD has already appeared, memory-type (M-SCM) based SSD has not been realistic yet due to the high memory cost. This paper proposes multi-SCM SSD with M-SCM as non-volatile cache of S-SCM to improve the SSD performance. In addition, the best configuration of multi-SCM SSD is discussed to balance the cost and the performance. As a result, the optimal capacity of M-SCM improves the SSD performance by up to 134% with 12% cost increase. If either M-SCM or S-SCM reaches the endurance limit, multi-SCM SSD cannot be used any longer. The optimal utilization scenario is that write erase (W/E) cycles of both M-SCM and S-SCM become their limits at the same time. To boost the SSD performance, the impact of omitting wear-leveling from both SCMs are investigated. As a result, the performance enhances by up to 28.2%. Additionally, effective wear-leveling policy is considered to balance both SSD performance and its lifetime.“