  At present, a major concern regarding data centers is their extremely high
energy consumption and carbon dioxide emissions. However, because of the
over-provisioning of resources, the utilization of existing data centers is, in
fact, remarkably low, leading to considerable energy waste. Therefore, over the
past few years, many research efforts have been devoted to increasing
efficiency for the construction of green data centers. The goal of these
efforts is to efficiently utilize available resources and to reduce energy
consumption and thermal cooling costs. In this paper, we provide a survey of
the state-of-the-art research on green data center techniques, including energy
efficiency, resource management, thermal control and green metrics.
Additionally, we present a detailed comparison of the reviewed proposals. We
further discuss the key challenges for future research and highlight some
future research issues for addressing the problem of building green data
centers.
