Scalability Analysis of Cloud Software Services

Cloud computing theoretically offers its customers unlimited cloud resources. However, the scalability of software services is often limited by their underlying architecture. In contrast to current scalability analysis approaches, we make work parameters, quality thresholds, as well as the resource space explicit in a conceptually consistent set of equations. We propose two scalability metric functions based on these equations. The resource scalability metric function describes the relation between the capacity of the multi-tier cloud software service and its use of cloud resources, whereas the cost scalability metric function replaces cloud resources with cost. We validate using the Cloud-Store application. CloudStore follows the TPC-W specification, representing an online book store. We have experimented with 21 different public Amazon Web Service configurations and two private OpenStack configurations.