ReSSD: A Software Layer for Improving the Small Random Write Performance of SSDs

摘要

Recently, NAND flash-based solid state drives (SSDs) have emerged as revolution ary storage media. Numerous studies have been carried out to employ SSDs in database systems and storage systems, motivated by SSD's attractive features such as decreased drive weight, increased shock resistance, low power consumption, and no seek latency. However, low-end SSDs targeting desktop and notebook environments show problem atic random write performance which is only comparable to or lower than that of HDDs This paper proposes a novel software layer called ReSSD whose purpose is to im prove the small random write performance of low-end SSDs with low memory usage. ReSSD works as a virtual block device on top of SSD which requires no modification neither in the operating systems nor in the applications. By inspecting all incoming re quests, ReSSD identifies small random writes which have potential to degrade SSD's performance significantly and transforms them into sequential and ordered-sequential writes which are more favorable to SSDs. Our evaluation results through Postmark and OLTP benchmarks show that the proposed approach accomplishes noticeable perform ance improvement on low-end SSDs under all workloads.