An auxiliary server threshold queueing model and its application to the operational characteristics of web server system

This paper analyzes an auxiliary server queueing model in which secondary servers are added to the main server(s) when the queue length exceeds some predetermined threshold value at the main queue. We model this system by the level-dependent quasi-birth-death (QBD) process and develop computation algorithms. We apply this model to the web-server system to explore some specific operational characteristics and draw some useful conclusions.