The power consumption of servers has to be reduced in a cluster to realize eco society. In this paper, we discuss power consumption models of servers. We take a macro level approach to reducing the total power consumption of servers to perform application processes. A server is equipped with a multi-core CPU. Through measuring electric power consumed by types of servers to perform application processes, we newly propose a multi-level power consumption (MLPC) model of a server with a multi-core CPU. Here, the power consumption of a server depends on the number of active cores and active threads where at least one application process is performed.
We also discuss a computation model which gives the expected execution time of a process on a server. Based on the MLPC model and the computation model, we discuss an energy-aware (EA) selection algorithm to select a server for each process requested by a client in a cluster so that the total electric energy consumption can be reduced. We evaluate the EA algorithm and show the total energy consumption is reduced in the EA algorithm compared with round-robin and random algorithms.