Performance Issues in Clouds: An Evaluation of Virtual Image Propagation and I/O Paravirtualization

As a technology, cloud computing has become an IT buzzword for the past few years. Cloud computing has often been used with synonymous terms such as software as a service, platform as a service, and infrastructure as a service (IaaS). Cloud computing has the potential to advance research discoveries by making data and computing resources readily available at an unprecedented economy of scale and with tremendous scalability. This paper discusses the importance of QoS and Iaas performance in cloud computing. The results of a quantitative evaluation are presented into the performance overheads of propagating virtual machine (VM) images to physical resources, at the Iaas layer and then accessing the images, via a Hypervisor's virtual block I/O device. Two virtual infrastructure managers are evaluated: Nimbus and OpenNebula, alongside two VM managers: XEN and KVM. Nimbus is found to outperform OpenNebula, while XEN outperforms KVM in the majority of cases. Conclusions are drawn from the results on the suitability of these technologies for data-intensive applications and applications requiring highly dynamic resource sets, where making an uninformed decision on what technology to use could prevent an application reaching its full potential, once deployed onto a cloud.