Rebirth-FTL: Lifetime optimization via Approximate Storage for NAND Flash

Abstract

The lifetime of NAND flash cells significantly degrades with feature-size reductions and multi-level cell technology. On the other hand, we have more and more approximate data such as images and video that can tolerate errors. In this paper, we propose Rebirth-FTL which reuses faulty blocks to store approximate data for the lifetime optimization. Rebirth-FTL efficiently and effectively manages two spaces with approximation-aware address mapping, coordinated garbage collection and differential wear leveling. We also develop a scheme to pass approximate information from userland to kernel space in Linux. Evaluation results show that Rebirth-FTL can significantly increase the lifetime by up to 3. 46X.