关键词: 计算机应用, 闪存, 数据库存储系统, 缓冲区替换算法, 生命值

Abstract: NAND flash memory is more and more widely applied in data storage systems. However, NAND flash memory has some inherent characteristics of asymmetric I/O latencies for read and write operations, erase-before-write and limited erase cycles, which are different from those of disk operations. So the existing traditional buffer algorithms for disk are not suitable for flash-based storage systems. Aiming to design an efficient buffer management policy for NAND flash memory, a life-aware buffer management algorithm named LAB-LRU is proposed, which manages the buffer by using three LRU lists. A life value is defined for each buffer page to enable active pages to stay longer in the buffer. The definition of the life value gives consideration of different access frequency, recency and the cost of flash read and write operations. Moreover, the multithreading technology is adopted to monitor the use of buffer size in parallel and evict dead pages in advance. A series of trace-driven simulations are carried out. The results show that the proposed LAB-LRU algorithm significantly outperforms the previous best-known algorithms in terms of the buffer hit ratio, the numbers of flash write and read operations and the overall runtime.

Key words: computer application, flash, database storage system, buffer management algorithm, life value