  We formulate a control problem for a GI/GI/N+GI queue, whose objective is to
trade off the long-run average operational costs (i.e., abandonment costs and
holding costs) with server utilization costs. To solve the control problem, we
consider an asymptotic regime in which the arrival rate and the number of
servers grow large. The solution to an associated fluid control problem
motivates that non-idling service disciplines are not in general optimal,
unless some arrivals are turned away. We propose an admission control policy
designed to ensure servers have sufficient idle time that we show is
asymptotically optimal.
