Elsevier Editorial System(tm) for Journal of Systems and Software Manuscript Draft Title: a Goal-oriented Simulation Approach for Obtaining Good Private Cloud-based System Architectures a Goal-oriented Simulation Approach for Obtaining Good Private Cloud-based System Architectures

Highlights? We show one way of rationally coming up with a suitable design for a private cloud. ? Stakeholder goals are identified early, analyzed and used to drive the proposed process. ? Cloud Computing simulations are used iteratively and in an interleaving manner to evaluate design decisions. ? The proposed approach borrows heavily from existing techniques in Software Engineering. The fast-growing Cloud Computing paradigm makes it possible to use unprecedented amounts of computing resources at lower costs, among other benefits such as fast provisioning and reliability. In designing a good architecture - the numbers, types and layouts of devices - for a cloud-based system, which meets the goals of all stakeholders, such goals need to be factored in from the earliest stages. However, there seems to be a lack of methodologies for incorporating stakeholder goals into the design process for such systems, and for assuring with higher confidence that the designs are likely to be good enough for the stated goals. In this paper, we propose a goal-oriented simulation approach for cloud-based system design whereby stakeholder goals are captured, together with such domain characteristics as workflows, and used in creating a simulation model as a proxy for the cloud-based system architecture. Simulations are then run, in an interleaving manner, against various configurations of the model as a way of rationally exploring, evaluating and selecting among incrementally better architectural alternatives. We illustrate important aspects of this approach for the private cloud deployment model and report on our experiments, using a smartcard-based public transportation system.