一种基于SSD缓存的RAID5/6写优化技术研究  

Exploring the Potential of HDD-based RAID 5/6 Write Optimization in the SSD Cache

作　　者：詹玲 吴畏 王方 朱承浩 万继光[3] ZHAN Ling;WU Wei;WANG Fang;ZHU Cheng-hao;WAN Ji-guang(Division of Information Science and Technology,Wenhua University,Wuhan 430074,Chin;China Ship Development and Design Center,Wuhan 430064,China;Wuhan National Laboratory of Optoelectronics,Huazhong University of Science ＆ Technology,Wuhan 430074,China)

机构地区：[1]文华学院信息学部计算机系,武汉430074 [2]中国舰船研究设计中心,武汉430064 [3]华中科技大学武汉光电国家实验室,武汉430074

出　　处：《小型微型计算机系统》2018年第10期2226-2232,共7页Journal of Chinese Computer Systems

基　　金：湖北省自然科学基金面上项目(2018CFB774)资助

摘　　要：基于SSD与磁盘混合结构具有很好的性价比,是存储研究的一个重要方向,本文针对使用SSD做RAID缓存的结构,提出了一种利用SSD缓存保留区中无效数据来优化RAID写性能的技术.根据SSD的物理特性,写请求的数据被写到空白的数据页上,而原来的旧数据被置为无效数据,存在SSD的保留区中等待垃圾回收.本文采用延迟擦除这些无效数据的方法,将其用于优化RAID5/6小写时的校验更新操作,通过在校验更新时从SSD中读取旧数据来减少磁盘操作次数,从而提高系统性能.本文也对该设计技术进行了实现与测试,实验结果表明,在缓存采用写回模式下,改进后系统平均写响应时间要比原来减少了10. 13%到16. 17%,而在写穿模式下响应时间可以减少16. 67%到21. 32%.Considering the cost efficiency, SSD-HDD hybrid storage systems have got plenty proposed improvements, , in this paper, we propose using SSDs as the cache, and utilizing invalid data stored in the SSD over-provisioning space to optimize small write performance of HDD-based RAID 5/6 systems. As data pages being updated in SSDs, out-of-date data pages are invalidated and chosen for later SSD internal garbage collections and finally for erasure. Our idea is to selectively delay the erasure of out-of-date pages and keep these otherwise useless out-of-date data in SSD contribute to RAID 5/6 parity computations upon write I/Os, therefore we reduce HDD I/Os for parity updating and boost HDD-based RAID 5/6 performance. Experimental results show that, under the writeback mode, our proposal improves the average response time by 10.13% ～ 16.17%, under the write-through mode, improvement for the average response time by 16.67% ～ 21.32%, respectively.

关 键 词：磁盘阵列 固态硬盘 缓存算法 垃圾回收 

分 类 号：TP333[自动化与计算机技术—计算机系统结构]