ABSTRACT
During recent years, cloud computing has become more and more popular and many IT giants, such as IBM[1], Microsoft[2], Amazon[3], have promoted their cloud computing plans. There are also many open source platforms in this field, like OpenStack[4], CloudStack[5], and Eucalyptus[6]. As one of the most successful IaaS communities, OpenStack attracts so much contributions from many companies and scholars. In IaaS platform, the virtual machine scheduling algorithm, determines in which hosts the requested virtual machine should be placed. This algorithm has one important and fatal issue, which has great influence on the quality and robustness of the cloud system, such as response time, resource utilization rate, load balance, total revenue of the system, etc.
