This paper discusses the challenges and the possibilities offered by controlling a data center as a node of the smart-grid. Communication between the grid and a data center takes the form of a time-varying and power-consumption-dependent electricity price. A cyber-physical approach is considered. The computational and the physical characteristics of a data center, as well as the interactions between the two aspects, are explicitly represented. Simulation results show that the proposed control approach can lead to larger income for data center operators than other approaches that do not consider the interactions between the cyber and the physical subsystems.