Profiling-Based Log Block Replacement Scheme in FTL for Update-Intensive Executions

FTL (Flash Translation Layer) hides details of flash memory, providing file systems with an abstract view of the flash memory. For NAND flash memory, some previous researches have achieved dramatic performance enhancement by adopting log-based FTL, which records time-consuming write operations in log blocks, rather than executes them immediately. Log block replacement scheme plays an essential role in this method, due to the limitation of pre-reserved log block space, this method entails selecting some victims from the existing blocks and re-use them for newly issued operations. However, simple replacement algorithms are vulnerable to select such log blocks that will be used soon, which causes performance degradation. In this paper we propose a smarter log block replacement scheme to alleviate this problem by keeping busy log blocks from being selected, based on profiling and analyzing log block status. We show that our scheme reduces unnecessary time-consuming write operations and achieves performance improvement especially for the applications having intensive locality.