Song have studied the problem of the efficient resource allocation in multiapplication virtualized data centers. The objective is to improve the utilization of resources leading to the reduced energy consumption. To ensure the QoS, the resources are allocated to applications proportionally according to the application priorities. Each application can be deployed using several VMs instantiated on different physical nodes. In resource management decisions, only the CPU and RAM utilizations are taken into account. In cases of limited resources, the perfor- mance of a low-priority application is intentionally degraded and the resources are allocated to critical applications. The authors have proposed scheduling at three levels: the application-level scheduler dispatches requests among application’s VMs; the local level scheduler allocates resources to VMs running on a physical node according to their priorities; and the global-level scheduler controls the resource “flow” among the applications. Rather than apply VM migration to implement the global resource “flow,” the authors preinstantiate VMs on a group of physical nodes and allocate fractions of the total amount of resources assigned to an application to different VMs.