Delay performance of data-center queue with setup policy and abandonment

Abstract

This paper considers a finite capacity multiserver queue for performance modeling of data centers. One of the most important issues in data centers is to save energy of servers. To this end, a natural policy is to turn off a server immediately once it has no job to process. In this policy, which is called ON–OFF policy, the server must be setup upon the arrival of a new job. During the setup time, the server cannot process jobs but consumes energy. To mitigate the drawback, this paper considers a setup policy, where the number of setup servers at a time is limited. We also consider an extension of the setup policy in which some of servers, but not all of them, are allowed to remain idle for a random amount of time. The main purpose of this paper is to analyze the delay distribution of the multiserver queue with the setup policies. We assume that jobs may abandon the queue without receiving their services. We formulate the queue length process using a two-dimensional continuous-time Markov chain. It can be shown that we cannot apply the distributional Little’s law to obtain the waiting time distribution via the queue length distribution. Therefore, we construct a three-dimensional absorbing Markov chain which describes the virtual waiting time process. We then obtain a phase-type expression of the stationary waiting time distribution. We evaluate the performance of the multiserver queue with the setup policy, and then discuss the optimal control parameters of the policy based on the delay performance as well as the mean power consumption.