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This paper presents a space reuse strategy for flash translation layers in SLC nand flash storage systems. The basic idea is to prevent a block with many free pages from being erased in a merge operation. The preserved blocks are further reused as replacement blocks. In such a way, the space utilization and the number of erase counts of each block in a nand flash are enhanced. By employing the reuse strategy, we propose a reuse-aware flash translation layer (FTL) called reuse-aware NFTL (RNFTL) to improve the endurance and space utilization of single level cell (SLC) nand flash. We provide the performance analysis of RNFTL for frequent update operations and sequential write operations, and theoretically compare RNFTL with representative FTL schemes. We also discuss the opportunity to apply the reuse strategy in log-block-based FTL schemes. To the best of our knowledge, this is the first work to employ a space reuse strategy in FTLs to improve the space utilization and endurance of nand flash. The experiments have been conducted on a set of traces collected from real workload in daily life. The results show that the space reuse strategy can effectively improve space utilization, block lifetime and wear-leveling compared with the previous work.
Very Large Scale Integration (VLSI) Systems, IEEE Transactions on (Volume:20 , Issue: 6 )
Date of Publication: June 2012