固態硬碟上隨機存取效能之探討

A Survey of Random access Performance on flash Drive

陳郁婷(Chen, Yuting)

指導教授 ： 羅習五

國立中正大學/工學院/資訊工程學系/碩士(2012年)

摘要

當資料具有隨機存取的性質時，如果我們使用傳統硬碟作為存儲裝置，那麼當需要的資料與目前讀寫頭的位置有很大距離，將會耗費很多時間。然而，在固態硬碟上卻不會有這種現象，所以一般具有隨機存取性質的資料會存在固態硬碟中，而且固態硬碟具有非揮發性、低耗電、抗震性、存取快速等優點。
雖然固態硬碟中 sequential access 和random access的效能每年都有提升，但是write/read操作的sequential 和random改善的比值卻受到限制。本論文將著重於FTL(flash translation layer)此階層對random I/O效能的改善。我們將FTL演算法分為direct mapping和log-based mapping以及demand-based mapping三種類別。並且我們藉由分析random access的效能，說明不同演算法的利弊得失。

關鍵字

固態硬碟 ； 快閃記憶體 ； 隨機存取

並列摘要

The performance of sequential access and random access of SSDs (solid-state disks) is improved every year, but the improved ratios of read/write operations are limited. The focus of this thesis is to survey how a flash translation layer (FTL) improves the performance of random I/O. We group various algorithms of FTL into three categories named direct mapping, log-based mapping and demand-based mapping schemes. An analysis of random access performance is given to illustrate the benefits and costs of different algorithms.

並列關鍵字

SSD ； flash ； random access

參考文獻

[2] L. P. Chang, "Hybrid solid-state disks: Combining heterogeneous NAND flash in large SSDs,"in Proc. ACM/IEEE Asia and South Pacific Design Automation Conf. (ASPDAC '08) , March 2008, pp. 428-433.

[5] T. S. Chung, D. J. Park, S. Park, D. H. Lee, S. W. Lee and etc., “A survey of flash Translation Layer,” Elsevie Journal of Systems Architecture (JSA), vol. 55, no. 5-6, 2009.

[6] S. Lee, D. Shin, Y. J. Kim and J. Kim, "LAST: locality-aware page translation for NAND flash memory-based storage systems," in Proc. SIGOPS Architectural Support for Programming Languages and Operating Systems (ASPLOS'08), Oct. 2008, pp. 36-42.

[7] C. Wang and W. F. Wong, "ADAPT: Efficient workload-sensitive flash management based on adaptation prediction and aggregation," in Proc. IEEE Mass Storage Systems and Technologies (MSST), April 2012, pp. 1-12.

[8] J. Kim, J. M. Kim, S. H. Noh, S. L. Min and Y. Cho, "A space-efficient flash translation layer for Compactflash systems,"IEEE Transactions on Consumer Electronics, vol. 48, no. 2, pp. 366-375, May 2002.