ABSTRACT
Virtualization is an effective technique for maximizing the utilization of physical servers (hosts) in an Infrastructure-as-a-Service (IaaS) cloud data center, with a number of virtual machines (VMs) running on a given host [7]. Furthermore, energy expenditure of such servers can be minimized by pooling of hosts [8]. In this approach, servers are partitioned into a hot pool (always on and with VMs instantiated and ready to run), a warm pool (on but without VMs instantiated), and a cold pool with hosts turned off. Servers are, then, moved from one pool to another as needed to fulfill user requests or to conserve energy.
