Bitmap Discard Operation for the higher utilization of Flash Memory Storage

Abstract

NAND Flash memory storage is widely used in computing systems. In General, there exists mismatch between logical address and physical address in Flash storage, and these address translations are managed by Flash Translation Layer(FTL). Due to its management, logically invalid data is considered as physically valid at some parts in Flash device, which causes additional overhead. The physically valid area being logically invalid area can be invalidated by TRIM or discard command, however, too many discard commands degrade throughput. In this paper, we propose a bitmap-based discard operation which can decrease the number of runtime discard commands. According to the proposed scheme, hundreds of separated region can be discarded all at one bitmap-based discard command.