Increasing the Lifetime of Flash Memory Based SSDs by Improving the Merge Operation in Flash Translation Layer

Abstract

The impressive features of Solid-State Drives (SSDs) have made them be used in a wide range of storage systems. NAND Flash memory, as a good choice for SSDs, caused many challenges. The impossibility of data overwritten in this type of memories is their biggest challenge since this constraint ultimately leads to a decrease in memory lifetime. Numerous designs have been developed to overcome the above challenge in the interface layer of flash memories known as Flash Translation Layer (FTL). In this paper, we present a new FTL that aims to improve the lifetime of memory based on an equation. Using this equation, two major challenges in SSDs can be targeted simultaneously and both can be improved. Reduction of the number of unused pages erased in merge operations and simultaneous increase of the number of invalid pages released in the Garbage Collection (GC) operations, are two of the achievements of our proposed FTL. The results of evaluation on real workloads indicate that parameters of unused erased pages decreased by 5% to 11%, invalid pages released increased by 10% to 28%, redundant written pages in garbage collection operations decreased by 8% to 25% and finally the number of erased blocks decreased by 3% to 12%. Therefore, the significant improvement of these four parameters has a direct impact on the memory lifetime.