A Two-Level Caching Mechanism for Demand-Based Page-Level Address Mapping in NAND Flash Memory Storage Systems

The increasing capacity of NAND flash memory leads to large RAM footprint on address mapping in the Flash Translation Layer (FTL) design. The demand-based approach can reduce the RAM footprint, but extra address translation overhead is also introduced which may degrade the system performance. This paper proposes a two-level caching mechanism to selectively cache the on-demand page-level address mappings by jointly exploiting the temporal locality and the spatial locality of workloads. The objective is to improve the cache hit ratio so as to shorten the system response time and reduce the block erase counts for NAND flash memory storage systems. By exploring the optimized temporal-spatial cache configurations, our technique can well capture the reference locality in workloads so that the hit ratio can be improved. Experimental results show that our technique can achieve a 31.51% improvement in hit ratio, which leads to a 31.11% reduction in average system response time and a 50.83% reduction in block erase counts compared with the previous work.