SSKIP: Lifetime Aware Page Skipping for Multi-Level Cell Flash-based Solid-State Drives

Abstract

NAND flash memory-based solid-state drives (SSDs) have been increasingly used in storage systems. Compared to single-level cell (SLC) NAND, which stores 1 bit per cell, multi-level cell (MLC) NAND stores 2 or more bits per cell, enabling higher-capacity and lower-cost SSDs. However, MLC NAND has inferior write performance compared to SLC NAND. A method to improve the write performance is to exploit the performance variability in MLC flash memory by skipping the slow pages (i.e., data writes always served by fast pages). However, excessive page skips cause the free space of the SSD to be consumed quickly, harmful to the SSD performance and lifetime. In this paper, a selective page skip mothed called SSKIP is proposed to improve the MLC write performance while maintaining the target SSD lifetime. According to the performance results, SSKIP can improve the performance by up to 56% by performing page skips. Moreover, it prevents violating the target lifetime warranty due to excessive page skips.