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NAND flash memories have been used in many mobile consumer devices as storage media because they are small, fast, shock-resistant, and energy-efficient. However, the flash storage systems based on these flash devices need a special software layer, the FTL, to translate logical addresses from a host system to physical addresses in NAND flash memories. Recently, the flash storage systems in mobile devices tend to employ a page-level mapping scheme as they are required to yield higher access bandwidth. Unlike common SSDs, which often keep the majority of mapping information in fast but volatile DRAM, the flash storage systems in mobile consumer devices keep only a limited subset of mapping information in a small-sized SRAM due to the restrictions in size, cost, and power consumption. For this reason, many cache management schemes proposed for SSDs may not be suitable for the flash storage systems in mobile consumer devices, though most map cache management schemes used in mobile storage are basically designed for SSD. This paper proposes a novel cache management scheme targeting mobile consumer devices. The proposed scheme uses different management granularities in allocating and evacuating cache space. Experimental results show that the proposed scheme improves map cache performance by up to 36% compared to the existing cache management techniques.

NAND flash memory has been widely used as a storage medium in mobile devices, PCs, and workstations due to its advantages such as low power consumption, high performance, and random accessability compared to a hard disk drive. However, NAND flash cannot support in-place update so that it is mandatory to erase the entire block before overwriting the corresponding page. In order to overcome this drawback, flash storages need a software support, named Flash Translation Layer. However, as the high performance mass NAND flash memory is getting widely used, the size of mapping tables is increasing more than the limited DRAM size. In this paper, we propose an adaptive mapping information caching algorithm based on page mapping to solve this DRAM space shortage problem. Our algorithm uses a mapping information caching scheme which minimize the flash memory access frequency based on the analysis of several workloads. The experimental results show that the proposed algorithm can increase the performance by up to 70% comparing with the previous mapping information caching algorithm.