Is your cloud elastic enough? Performance modeling the elasticity of infrastructure as a service (IaaS) cloud applications

Elasticity, the ability to rapidly scale resources up and down on demand, is an essential feature of public cloud platforms. However, it is difficult to understand the elasticity requirements of a given application and workload, and if the elasticity provided by a cloud provider will meet those requirements. We introduce the elasticity mechanisms of a typical Infrastructure as a Service (IaaS) cloud platform (inspired by Amazon EC2). We have enhanced our Service Oriented Performance Modeling method and tool to model and predict the elasticity characteristics of three realistic applications and workloads on this cloud platform. We compare the pay-as-you-go instance costs and end-user response time service level agreements for different elasticity scenarios. The model is also able to predict the elasticity requirements (in terms of the maximum instance spin-up time) for the three applications. We conclude with an analysis of the results.