Over the past few years, energy provisioning in server farms and data-centres has become an active area of research. As such, many models have been proposed where an individual server has setup times and can switch between two different energy states (on and off). To make such models tractable, assumptions are usually made on the type of policies the system can implement. However, it is often not known if such assumptions allow for the model to capture the optimal policy, or if such a model will be strictly suboptimal. In this work we model such systems using Markov Decision Processes (MDPs) and derive several structural properties which (partially) describe the optimal policy. These properties reduce the set of feasible policies significantly, allowing one to describe the optimal policy by a set of thresholds which have considerable structure. In addition to the analysis, we discuss the current literature in the context of our results.
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