A single server queue with workload-dependent service speed and vacations

In modern data centers, the trade-off between processing speed and energy consumption is an important issue. Motivated by this, we consider a queueing system in which the service speed is a function of the workload, and in which the server switches off when the system becomes empty, only to be activated again when the workload reaches a certain threshold. For this system we obtain the steady-state workload distribution. We use this result to choose the activation threshold such that a certain cost function, involving holding costs and activation costs, is minimized.