连续媒体层次存储中磁带库调度收益分析

Scheduling benefits analysis of tape libraries in hierarchical storage-based continuous media applications

层次存储技术是存储和管理海量连续媒体数据的有效手段。I/O请求的调度是层次存储研究中的重要问题,目前也有很多的调度算法,但它们之间缺乏定量的分析和对比,使得调度算法的选择缺少可靠的依据。该文利用排队论对调度收益进行定量分析,分析了它与系统平均队长等因素的定量关系,并得到调度在平均等待时间上的收益与原始等待时间的关系,指出它们近似成二次曲线关系。仿真试验表明了这些结论的有效性,它对于层次存储管理系统中,I/O请求调度算法的选择具有很好的指导作用。

Hierarchical storage technology is an effective way to store massive continuous media objects. I/O requests for scheduling in tertiary storage devices, such as a tape library, are one of the key problems in hierarchical storage systems. Although there are many scheduling algorithms, few give a quantitative method to evaluate different algorithms. This paper analyzes the scheduling problem using queuing theory to find a correlation between the scheduling benefit gained from the reduction of the all mean waiting time and the initial waiting time. The analysis results are proved by simulations and can be used as guidelines for selecting a scheduling algorithm for system implementation.