Abstract: Compared with traditional hard disk drives (HDDs),NAND-Flash-based solid-state drives (SSDs) are non-volatile and can provide better performance as well as lower power consumption.Therefore,they have achieved extensive application in data centers,cloud computing and online transaction trading,etc.However,in NAND Flash memory,the speed of read operation is significantly faster than the write operation.Hence,for a concurrent workload with a mixture of read and write requests,reads may be blocked by writes,which exhibites an enormous read latency.In many read-intensive applications,especially the online transaction trading,in which the proportion of read requests is than 90%,the sharp increase of the read latency influences the overall performance of the system severely.In this paper,we proposed a read-write performance optimization scheduling scheme which achieves remarkable improvement about the read performance by dynamically adjusting the priority sequence of read and write requests beneath the flash translation layer.In the experiment,we designed and built an SSD simulator to evaluate the effectiveness of the scheduling scheme.Experimental results show that by implementing the proposed scheme,the maximum and the average read latency in the system are substantially reduced,with the reduction of 72% and 41%,respectively.

Key words: Flash memory,SSD,Data scheduling,Queue management