A Framework for QoS-Aware Execution of Workflows over the Cloud

The Cloud Computing paradigm is providing system architects with a new powerful tool for building scalable applications. Clouds allow allocation of resources on a ”pay-as-you-go” model, so that additional resources can be requested during peak loads and released after that. In this paper we describe SAVER (qoS-Aware workflows oVER the Cloud), a QoS-aware algorithm for executing workflows involving Web Services hosted in a Cloud environment. SAVER allows execution of arbitrary workflows subject to response time constraints. SAVER uses a simple Queueing Network (QN) model to identify the optimal resource allocation; specifically, the QN model is used to identify bottlenecks, and predict the system performance as Cloud resources are allocated or released. Our approach has been validated through numerical simulations, whose results are reported in this paper.