Performance Modelling and Simulation of Three-Tier Applications in Cloud and Multi-Cloud Environments

A significant number of Cloud applications follow the 3-tier architectural pattern. Many of them serve customers worldwide and must meet non-functional requirements such as reliability, responsiveness and Quality of Experience (QoE). Thus the flexibility and scalability offered by clouds make them a suitable deployment environment. Latest developments show that using multiple clouds can further increase an application’s reliability and user experience to a level that has not been achievable before. However, the research in scheduling and provisioning 3-tier applications in clouds and across clouds is still in its infancy. To foster the research efforts in the area, we propose an analytical performance model of 3-tier applications in Cloud and Multi-Cloud environments. It takes into account the performance of the persistent storage and the heterogeneity of cloud data centres in terms of Virtual Machine (VM) performance. Furthermore, it allows for modelling of heterogeneous workloads directed to different data centres. Based on our model, we have extended the CloudSim simulator, through which we validate the plausibility of our approach. The conducted experiments with the RUBiS workload show that the predicted performance characteristics by the simulation approximate well those of the modelled system