CFTL: A Convertible Flash Translation Layer with Consideration of Data Access Patterns

NAND flash memory-based storage devices are increasingly adopted as one of the main alternatives for magnetic disk drives. The flash translation layer (FTL) is a software/hardware interface inside NAND flash memory, which allows existing disk-based applications to use it without any significant modifications. Since FTL has a critical impact on the performance of NAND flash-based devices, a variety of FTL schemes have been proposed to improve their performance. However, existing FTLs perform well for either a read intensive workload or a write intensive workload, not for both of them due to their fixed and static address mapping schemes. To overcome this limitation, in this paper, we propose a novel FTL addressing scheme named as Convertible Flash Translation Layer (CFTL, for short). CFTL is adaptive to data access patterns so that it can dynamically switch the mapping of a data block to either read-optimized or write-optimized mapping scheme in order to fully exploit the benefits of both schemes. By judiciously taking advantage of both schemes, CFTL resolves the intrinsic problems of the existing FTLs. In addition to this convertible scheme, we propose an efficient caching strategy so as to considerably improve the CFTL performance further with only a simple hint. Consequently, both of the convertible feature and caching strategy empower CFTL to achieve good read performance as well as good write performance. Our experimental evaluation with a variety of realistic workloads demonstrates that the proposed CFTL scheme outperforms other FTL schemes.