DLSpace: Optimizing SSD Lifetime via An Efficient Distributed Log Space Allocation Strategy
DLSpace: Optimizing SSD Lifetime via An Efficient Distributed Log Space Allocation Strategy
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DLSpace：通过高效的分布式日志空间分配策略优化 SSD 寿命
DOI：
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发表时间：
2018
影响因子：
2
通讯作者：
谢长生
中科院分区：
文献类型：
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作者：
孙辉;黄建忠;秦啸;谢长生
由于有限数目的编程/擦除循环（即，P/E），过多的位置外更新和写前擦除操作在垃圾收集期间磨损这些P/E，这不利地缩短了固态盘（即，SSD）寿命。SSD的NAND闪存空间中的日志空间作为更新的页面缓冲区，这降低了垃圾收集频率，同时减少了P/E的消耗，以延长SSD的寿命。本文提出了一种新的分布式日志空间分配策略DLSpace，将日志空间划分为块级日志空间和页级日志空间，极大地优化了SSD的生命周期。DLSpaces日志页空间专用于数据块中的数据页。这样的日志页面空间只缓冲该数据块中的页面更新操作;从而使用日志块来推迟垃圾收集延迟。DLSpace有助于充分利用数据和日志块中的页面，以避免擦除具有空闲页面的块。因此，DLSpace通过减少在随机写入密集型工作负载下过多的有效页面重写和块擦除操作来降低写入放大。我们借助三个度量（即，写入放大、块擦除操作的数目以及第一垃圾收集发生之前的延迟时间）。实验结果表明，与现有的传统日志空间分配策略（即，TLSpace），DLSpace最大程度上分别将写入放大和擦除操作次数减少了55.2%和64.1%。DLSpace还将垃圾收集的TLSpaces延迟时间延长了73.3%，以优化SSD生命周期。
Due to limited numbers of program/erase cycles (i.e., P/Es) of NAND Flash, excessive out-of-place update and erase-before-write operations wear out these P/Es during garbage collections, which adversely shorten solid state disk (i.e., SSD) lifetime. The log space in NAND Flash space of an SSD performs as an updated pages buffer, which lowers garbage-collection frequency while reducing consumption of P/Es to extend SSD life-time. In this article, we propose DLSpace, a novel distributed log space allocation strategy named distributed log space, which divides log space into block-level log space and page-level log space to significantly opti-mize SSD lifetime. DLSpaces log page space is dedicated to data pages in a data block. Such log page space only buffers page-update operations in this data block; thereby the use of log blocks for postponing garbage collection delays. DLSpace is conducive to fully utilizing pages in data and log blocks to avoid erasures of blocks with free pages. Consequently, DLSpace decreases write amplification by reducing excessive valid page-rewrite and block-erase operations under random-write-intensive workloads. We carried out quantita-tive research on the extension of SSD lifetime by virtue of three metrics (i.e., write amplification, the number of block-erase operations, and the delay time before the first garbage collection occurring). Experimental results reveal that compared with the existing traditional allocation strategy for log space (i.e., TLSpace), DLSpace reduces write amplification and the number of erase operations by up to 55.2% and 64.1% to the most extent, respectively. DLSpace also extends TLSpaces delay time of garbage collections by 73.3% to optimize SSD lifetime.