SLAs in Virtualized Cloud Computing Infrastructures with QoS Assurance

Cloud Computing is gaining momentum as one of the technologies that promises to subvert our own idea of computing. With an increasing usage of cloud applications and their consequent dependency from connectivity, the nowadays Personal Computer is becoming merely a mobile device acting as a front-end to on-line applications and services. This huge paradigm shift in computing is witnessed for example by big market players who announced the imminent launch of innovative products and Operating Systems (like Chrome notebooks and the accompanying Chrome OS2. by Google), which are capable of projecting the user into the network in a few seconds by booting and starting immediately a web browser and (mostly) nothing else. In such a challenging scenario, more and more of the applications that we traditionally used locally on our PC are being hosted on cloud infrastructures and operated remotely through the Internet. This includes not only batch tasks, but also interactive applications which need to operate inherently with good levels of responsiveness. In this paper, the challenging problem is discussed of how to ensure predictable levels of Quality of Service (QoS) to cloud applications across the multiple layers of a typical cloud infrastructure, and how a reasonable Service Level Agreement (SLA) management and enforcement policy might look like. The scope of this paper represents a hands-on experience that was gained by the authors realising the IRMOS real-time cloud-computing infrastructure in the context of the IRMOS European Project.