Cloud computing represents a shift away from computing as a product that is purchased, to computing as a service that is delivered to consumers over the internet from large-scale data centers – or 'clouds'. This paper discusses some of the research challenges for cloud computing from an enterprise or organizational perspective, and puts them in context by… (More)
Cloud computing is the latest effort in delivering computing resources as a service. It represents a shift away from computing as a product that is purchased, to computing as a service that is delivered to consumers over the internet from large-scale data centres – or " clouds ". Whilst cloud computing is gaining growing popularity in the IT industry,… (More)
There is a rapid increase in the size of data centres (DCs) used to provide cloud computing services. It is commonly agreed that not all properties in the middleware that manages DCs will scale linearly with the number of components. Further, " normal failure " complicates the assessment of the performance of a DC. However, unlike in other engineering… (More)
Modern large-scale date centres, such as those used for cloud computing service provision, are becoming ever-larger as the operators of those data centres seek to maximise the benefits from economies of scale. With these increases in size comes a growth in system complexity, which is usually problematic. There is an increased desire for automated… (More)
We report on experiments exploring the interplay between the topol-ogy of the complex network of dependent components in a large-scale data-centre, and the robustness and scaling properties of that data-centre. In a previous paper  we used the SPECI large-scale data-centre simulator  to compare the robustness and scaling characteristics of… (More)
Network security is a concept which combines various business models and technologies together to deliver provisions and policies for comprehensive intrusion detection and unauthorized access. The only secured computer is the one with no power and no user. Any other computer can be compromised. Network Security is the most important issue for any… (More)
The trend for cloud computing has initiated a race towards data centres (DC) of an ever-increasing size. The largest DCs now contain many hundreds of thousands of virtual machine (VM) services. Given the finite lifespan of hardware, such large DCs are subject to frequent hardware failure events that can lead to disruption of service. To counter this,… (More)
We introduce Version 2 of SPECI, a system for predictive simulation modeling of large-scale data-centres, i.e. warehouse-sized facilities containing hundreds of thousands of servers, as used to provide cloud services.