A Business-Oriented Approach to the Design of Feedback Loops for Performance Management

This paper proposes an approach to automated enforcement of service level agreements (SLAs) by constructing information technology (IT) level feedback loops (e.g., admission control, CPU scheduling, load balancing) that achieve business objectives, especially maximizing SLA profits. We develop a framework in which profits are determined by revenues accrued for services delivered (e.g., completed transactions) and rebates to customers if services are unavailable or violate response time constraints. A methodology is described for profit-oriented controller design, and the methodology is applied to a Lotus Notes email server. The methodology relies heavily on modeling design choices to reduce the need for running live experiments. We show that simple linear models suffice to capture the dynamics of the email server we study, even for a time varying workload. In addition, our studies suggest that faster controllers (those with short settling times) consistently provide the best profits since they violate response time constraints less often and they do not sacrifice as much revenue. Last, our studies show that the selection of controller reference value has a significant impact on profits.