Understanding intrinsic characteristics and system implications of flash memory based solid state drives
Understanding intrinsic characteristics and system implications of flash memory based solid state drives
复制标题
DOI：
10.1145/1555349.1555371
复制
发表时间：
2009-06
期刊：
影响因子：
--
通讯作者：
Feng Chen;David A. Koufaty;Xiaodong Zhang
中科院分区：
文献类型：
--
作者：
Feng Chen;David A. Koufaty;Xiaodong Zhang
基于闪存的固态硬盘 (SSD) 被称为一项可以彻底改变数据存储系统的“关键技术”。由于 SSD 在物理和逻辑上与传统硬盘驱动器 (HDD) 共享通用接口，因此将 SSD 有效集成到存储层次结构中非常重要。然而，SSD 硬件实现的细节往往隐藏在如此狭窄的接口后面。事实上，由于 SSD 控制器固件通常必然采用复杂的算法，因此 SSD 中的性能动态预计会比 HDD 系统更复杂。大多数有关 SSD 的现有文献或产品规范仅提供高级描述和标准性能数据，例如带宽和延迟。为了深入了解SSD独特的性能特征，我们对从低端到高端产品的不同类型的最先进SSD进行了深入的实验和测量。我们观察到 SSD 的一些意外性能问题和不确定行为，这些问题尚未在文献中报道过。例如，我们发现碎片可能会严重影响性能，在最近发布的 SSD 上，碎片会影响性能的 14 倍以上。此外，与 SSD 访问与访问模式不相关的普遍看法相反，我们发现读取和写入的性能与数据访问的随机性之间存在很强的相关性。在最坏的情况下，平均延迟可能会增加 89 倍，而带宽可能会降至仅 0.025MB/秒。我们的研究揭示了 SSD 技术性能动态中的几个意想不到的方面，系统设计人员和数据密集型应用程序用户必须解决这些问题，以便有效地将其放置在存储层次结构中。
Flash Memory based Solid State Drive (SSD) has been called a "pivotal technology" that could revolutionize data storage systems. Since SSD shares a common interface with the traditional hard disk drive (HDD), both physically and logically, an effective integration of SSD into the storage hierarchy is very important. However, details of SSD hardware implementations tend to be hidden behind such narrow interfaces. In fact, since sophisticated algorithms are usually, of necessity, adopted in SSD controller firmware, more complex performance dynamics are to be expected in SSD than in HDD systems. Most existing literature or product specifications on SSD just provide high-level descriptions and standard performance data, such as bandwidth and latency. In order to gain insight into the unique performance characteristics of SSD, we have conducted intensive experiments and measurements on different types of state-of-the-art SSDs, from low-end to high-end products. We have observed several unexpected performance issues and uncertain behavior of SSDs, which have not been reported in the literature. For example, we found that fragmentation could seriously impact performance -- by a factor of over 14 times on a recently announced SSD. Moreover, contrary to the common belief that accesses to SSD are uncorrelated with access patterns, we found a strong correlation between performance and the randomness of data accesses, for both reads and writes. In the worst case, average latency could increase by a factor of 89 and bandwidth could drop to only 0.025MB/sec. Our study reveals several unanticipated aspects in the performance dynamics of SSD technology that must be addressed by system designers and data-intensive application users in order to effectively place it in the storage hierarchy.