Abstract: To reduce the time and cost of workflow scheduling in cloud computing,we proposed a bi-directional scheduling algorithm including two sub-algorithms,which are Backward and Forward.Firstly,the Backward algorithm achieve a scheduling according to the deadline start time for each task scheduling.Then,to reduce the cost of scheduling,the Forward algorithm schedules each task in advance as much as possible.In the process of forward scheduling,taking the deadline and the biggest cost and transmission time into consideration,the algorithm achieves dynamic scheduling.The experiment results show that our algorithm is better than BDA algorithm and ICPCP algorithm for lower rent cost and higher scheduling flexibility.

Key words: Cloud computing,Virtual machine,Workflow,Bi-directional scheduling