面向闪存存储的公平高效I/O调度器

Fair and Efficient I/O Scheduler for Flash Storage

固态硬盘(SSD)具有优秀的读写性能,逐渐被广泛使用在存储系统中。而传统的I/O调度算法都是针对磁盘进行优化,Linux NOOP调度器延时低,却不能保证I/O公平性;CFQ调度器实现了I/O公平性却牺牲了响应性。为了针对SSD实现公平高效的I/O调度策略,本文提出一种全新的I/O调度器—SSDCFQ。SSDCFQ结合CFQ和NOOP调度算法的优点,并且为了加速读写过程引入元数据请求队列,为每个进程维护两个FIFO请求队列,并通过round-robin轮询策略进行管理。实验结果表明,SSDCFQ比NOOP的公平性提高了28%,比CFQ的延时降低了55%。

Solid State Drive（ SSD） is widely used in storage systems nowadays due to its outstanding performance. However,traditional I/O schedulers are designed for Hard Disk Drive（ HDD） only. NOOP scheduler achieves low latency but cannot provide fairness of I/O bandwidth,while CFQ scheduler guarantees fairness at the expense of responsiveness. In order to achieve a fair and efficient I/O scheduler for SSD,this paper proposes a new scheduler called SSDCFQ,which combines the advantages of CFQ and NOOP scheduler.Besides,we introduce metadata request queue to accelerate I/O scheduling. SSDCFQ maintains two FIFO request queues for each process,and it manages them with round-robin scheme. Experiments show that,SSDCFQ improves fairness by 28% compared to NOOP,meanwhile reduces latency by 55% compared to CFQ.