SEPL: Smart Evicted Page List Buffer for NAND Flash Storage System

NAND flash memory has become popular in the consumer market while its success in main storage market is still limited. One of the reasons is that NAND flash suffers severe performance degradation under random write requests, and these requests are inevitable since the complexity of the applications is growing rapidly. One way to mitigate the problem is by applying DRAM as the buffer between host and NAND flash to absorb these requests, and numbers of buffer management schemes such as CFLRU and FARS had been proposed. However, these algorithms do not respect write intensive and long-term pages enough. In this paper, we propose a buffer replacement algorithm with a smart eviction list and a brand new eviction criterion that helps retaining the write intensive pages in the buffer in order to lower down the number of write request into NAND flash memory. Experiments show that SEPL outperforms other algorithms in the traces where random access is dominant.