Managing performance and power consumption in a server farm

We examine the problem of managing a server farm in a way that attempts to satisfy the conflicting objectives of high performance and low power consumption. A subset of servers is designated as ‘reserve’. The reserves are powered up when the number of jobs in the system is sufficiently high, and are powered down when that number is sufficiently low. Powering up takes an interval of time during which the reserves consume power but do not serve jobs. The question of how to choose the number of reserves, and the up and down thresholds, is answered by analyzing a suitable queueing model and minimizing an appropriate cost function. Heuristics and numerical results are also presented.     

An intermittently served discrete time queue with applications to meteor scatter communications

A discrete time single server queue with service interruptions is analyzed in the steady-state under general assumptions. The main motivation for the study is the performance evaluation of a communication protocol using ionized layers created by meteors. The analysis yields the joint distribution of the queue size and the remaining duration of the current operative or inoperative period. The solution takes a particularly simple form in the case where the operative periods have a rational generating function.On short-term visits to the University of Newcastle upon Tyne and AT&T Bell Laboratories.Work done while the author was visiting the AT&T Bell Laboratories.