固態硬碟的效能評測與分析方法

Abstract

固態硬碟使用快閃記憶體作為儲存媒體,因此具有省電,耐震,以及優異的隨機存取能力,近年來已經展現出取代傳統磁碟的趨勢.固態硬碟的廠商經常宣稱其產品有優異的效能,但是使用者的感受卻不是如此而抱怨不斷,問題的原因是廠商沿用了傳統磁碟的測試工具,其典型的循序與隨機存取得到的測試結果,並沒有辦法反應固態硬碟的管理成本,因此並不能代表固態硬碟實際的效能.我們提出了一個基於實際存取行為的固態硬碟效能評測與分析方法.我們收集了8種在個人電腦上常見的Workload進行特徵分析,將具有相似特徵的Workload集合成Benchmark Suite,並且歸納這些特徵對固態硬碟管理議題造成的影響,使用者可以直接選用一組Benchmark Suite評估固態硬碟 的實際效能.

The base storage component of SSD is NAND Flash Memory, it has some advantages such as the high speed of read operation and shock resistance. On some application areas, SSD gradually replaces traditional hard drive disk becoming the major storage device of entire system. But the physical property of Flash Memory is Erase-before-Write, because of the erase-unit is much larger than the write-unit, we need take care of the random write pattern on SSD, otherwise the speed of write operation will degradation and become the bottleneck of entire system. Furthermore, due to disk fragmentation and applications of Multi-Thread, the write pattern will become more random, how to improve the problem of write throughput degradation on SSD caused by random write becoming more and more important. We proposed a new buffer management algorithm applied to SSD called HitStat, not only consider temporal locality and spatial locality simultaneously, but also adjust the Padding Threshold to better settings dynamically, much improve the write pattern written to NFTL. Finally, it shows about 30% enhancement of write throughput compared to FAB and BPLRU, which are other buffer management algorithms on SSD.