Performance and Cost-Effectiveness Analyses for Cloud Services Based on Rejected and Impatient Users

Cloud computing is an innovative service platform to offer diverse resources such as infrastructure, platform and software as services. However, one challenging aspect of such a service is the impatient user threat, which directly leads to numerous negative impacts such as poor throughput, unpredictable workload and waste of resources. In this paper, the problems of conducting system controls in a cost-effective way and simultaneously satisfying performance guarantees are first studied. System losses are analyzed according to the related performance factors and waiting buffer sizes. A cost model is developed to address a performances/cost tradeoff issue in which the user balking, reneging, system blocking and resources provisioning are all taken into account. The relationship between system controls and throughput variations in a multi-servers system with a finite buffer is demonstrated. A proposed policy combined with a heuristic algorithm allows cloud providers to control the service rate and buffer size within a system loss guarantee by solving constrained optimization problems. Simulation results show that more cost-saving and system throughput enhancement can be verified as compared to a system without applying our policy.