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The notion of cloud computing , where computing infrastructure, platforms, and software application services are offered at low cost from remote very-large-scale data centres accessed over the internet, is one that has recently received large amounts of attention in the IT industry. There have been predictions that this 'utility computing' will predominate in future with organisations discarding their internal servers in favour of applications accessible in the cloud . To service users, clouds clearly offer advantages in scalability, may reduce the costs of application management, and may reduce overall hardware costs. To service providers, they offer the opportunity to leverage existing data-centre infrastructure and to take advantage of the economies of scale available exclusively to purchasers of extremely large volumes of hardware and network capacity. While we think that some predictions of the costs savings from cloud adoption are optimistic, we are confident that cloud computing offers real business benefits. These will mean that more and more business and public-sector organisations will migrate some of their applications from dedicated servers to private or public clouds.This proposal extends the work of the existing EPSRC-funded Large-Scale Complex IT Systems (LSCITS) Initiative's research programme. The interests of the LSCITS Initiative in cloud computing are twofold: we argue that there is a need to provide analytical and predictive methods and tools that support decision making about the costs, benefits and risks of migrating applications to the cloud; and we believe that, because cloud data centres are instances of LSCITS, there are research challenges in their setting-up, operation, management and evolution while providing guaranteed levels of performance and dependability, quantified environmental impact, support for the development of scalable applications; and a range of resource pricing models.This proposal envisages a situation where enterprises are satisfied that cloud computing is a viable option for them and they wish to plan for a situation where a significant fraction of their LSCITS are deployed on the cloud. The deployment could be wholly outsourced on external shared enterprise clouds, such as those provided by IBM or HP or on a dedicated in-house managed facility, such as a hypothetical NHS cloud. Most likely, large organisations will have a mix of facilities using dedicated servers, an in-house cloud and external cloud providers. We will not tackle immediate short-term (2009) problems of cloud computing. Rather, we will focus on two, longer-term research themes, which are applicable to both data-centre design and application migration:1. Modelling and Simulation. We aim to develop simulation tools and techniques to help document, analyse and predict the attributes and behaviour of LSCITS where some or all of these systems are deployed in the cloud. These techniques will support application system and application portfolio modelling as well as the modelling of risks, pricing and the environmental impact of cloud-based systems.2. Dependability and Quality of Service We will explore how aspects of LSCITS such as dependability, resilience, and performance, are affected by the new benefits and vulnerabilities that arise from deploying systems in the cloud; we will explore methods for quantifying the degree to which these types of requirements are achieved and we will devise new theory and tools to help researchers and practitioners reason about the dependability and quality of service delivered by the cloud. We believe that these are important areas because cloud providers and enterprise users of cloud resources will require tools and techniques to inform their decision-making about the costs and risks of deploying business-critical systems on the cloud, and about the related issues of management, maintenance, and ongoing evolution.
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