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iSCSI虚拟交换机包转发调度算法FC-WFQ

韩永, 姚念民, 蔡绍滨, 陈金忠   

  1. 哈尔滨工程大学计算机科学与技术学院, 黑龙江哈尔滨 150001
  • 收稿日期:2012-03-15 修回日期:2012-08-10 出版日期:2013-03-25 发布日期:2013-03-25
  • 作者简介:韩 永 男,1982年4月生于山东省枣庄市.博士研究生,主要研究方向为网络存储的性能与安全. E-mail:hanyong@hrbeu.edu.cn; 姚念民 男,1974年9月生于黑龙江省大庆市.教授,博士生导师.主要研究方向为网络存储,无线传感器网络等. E-mail:yaonianmin@hrbeu.edu.cn
  • 基金资助:
    国家自然科学基金(No.61073047);中央高校基本科研业务费专项基金(No.HEUCFT1007,No.HEUCF100607)

Packet Forwarding Scheduling Algorithm FC-WFQ for iSCSI Virtualization Switch

HAN Yong, YAO Nian-min, CAI Shao-bin, CHEN Jin-zhong   

  1. College of Computer Science and Technology, Harbin Engineering University, Harbin, Heilongjiang 150001, China
  • Received:2012-03-15 Revised:2012-08-10 Online:2013-03-25 Published:2013-03-25

摘要: 与传统IP交换机不同,iSCSI虚拟交换机不仅实现IP数据包的转发,还应完成TCP、iSCSI和SCSI的协议处理.短包优先调度算法可保证iSCSI控制及命令PDU(Packet Data Unit)的优先传输,却未对该类数据包的转发带宽作出限制,该方法缺少针对iSCSI数据流特性的定量分析.通过排队理论建立iSCSI虚拟交换机转发iSCSI PDU过程的数学模型,然后提出一种iSCSI虚拟交换机的包调度算法FC-WFQ(Flow Control-WFQ),最后应用网络仿真软件ns-2建立仿真场景对交换系统进行测试.随着命令到达率以及命令中读写比例的变化,FC-WFQ对各数据流的转发带宽权重做相应的实时调整.实验结果显示,该调度算法可明显降低读写任务的平均响应时间,并显著提高iSCSI虚拟交换机的吞吐量.

关键词: SAN, SCSI, iSCSI虚拟交换机, 调度算法, WFQ, 排队模型

Abstract: Different from traditional IP switches,the iSCSI virtualization switch not only realizes the IP packets transmission,but also performs the processing of TCP,iSCSI and SCSI protocol.The short packet first scheduling algorithm insures the priority transmission of iSCSI command and status PDUs (Packet Data Unit),but does not impose restrictions on the forwarding bandwidth of such packets.Moreover,it is lack of quantitative analysis on iSCSI data flow characteristics for this method.The mathematical model of iSCSI PDUs forwarding process within the iSCSI virtualization switch was created by queuing theory.Then the packet scheduling algorithm called FC-WFQ (Flow Control-WFQ) was designed for the iSCSI virtualization switch used in the SANs.Finally the iSCSI virtualization switch with FC-WFQ was tested under certain network scenarios built by ns-2.In the experiments,while the command arrival rate and the ratio of read/write commands were changing,the FC-WFQ dynamically adjusted the forwarding bandwidth weight of each packet flow correspondingly.The results show that the scheduling algorithm can greatly reduce the mean response time of the read/write tasks,and significantly improve the throughput of the iSCSI virtualization switch.

Key words: SAN, SCSI, iSCSI virtualization switch, scheduling algorithm, WFQ, queuing model

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