By splitting up an underutilized physical host into several virtualized domains, Virtualization can make the optimal use of resources and reduce the energy consumption. By delving into the types of I/O applications, adjusting amount of resource, and combining different applications in one or more domains, several insights are observed in this paper: using a few exclusive physical CPU driver domain can improve the efficiency of forwarding, which makes over 17% performance improvement for I/O applications; in addition, the domain providing mixed services can achieve 70% performance gain, when compared with others that provide single service; last but not least, avoiding running too many network-provider domains simultaneously can relieve the inter-domain interference. These observations not only help to bring performance improvement to cloud consumers but also service stability to cloud providers.