云环境下周期和非周期混合实时任务双容错调度算法

Dual fault-tolerant scheduling algorithm of periodic and aperiodic hybrid real-time tasks in cloud environment

云环境中的处理机故障已成为云计算不可忽视的问题,容错成为设计和发展云计算系统的关键需求。针对一些容错调度算法在任务调度过程中调度效率低下以及任务类型单一的问题,提出一种处理机和任务主副版本分组的容错调度方法;并给出了副版本可重叠执行的判定方法,以及任务最坏响应时间的计算公式。通过实验和分析表明,和以前算法相比,将处理机分成两组分别执行任务主版本和任务副版本,减少了任务调度所需进行可调度测试的时间,增加了副版本重叠执行的机会,减少了所需的处理机个数,对提高系统处理机的利用率和容错调度的效率具有重要的意义。

The problem of cloud computing processors failure cannot be ignored in the cloud environment. Fault-tolerance becomes a key requirement in the design and development of cloud computing systems. Aiming at the problem of low scheduling efficiency and single type of task in most fault-tolerant scheduling algorithms, the fault-tolerant scheduling method based on processors, primary-backup copies of hybrid tasks grouped was proposed. A method to determine whether two backup copies can overlap was presented. What＇s more, the calculation formulas of periodic task worst-case response time and completion time of aperiodic tasks preemptive execution were given. The simulation result shows that the proposed algorithm has a remarkable saving of cloud computing system processors needed and scheduling computation time compared with Hybrid real time task Fault Tolerant Scheduling （HFTS） algorithm. It is of great significance for improving the reliability of cloud system and the schedulability of real-time tasks set, as well as the processor efficiency.