John O'Loughlin

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The performance of Cloud systems is a key concern, but has typically been assessed by the comparison of relatively few Cloud systems, and often on the basis of just one or two features of performance. In this paper, we discuss the evaluation of four different Infrastructure as a Service (IaaS) Cloud systems – from Amazon, Rackspace, and IBM – alongside a(More)
In this paper, we discuss the nature of variability in compute performance in Infrastructure Clouds and how this presents opportunities for Cloud Service Brokers (CSB) in relation to pricing. Performance variation in virtual machines of the same type and price raises specific issues for end users : (i) the time taken to complete a task varies with(More)
To some the next iteration of Grid and utility computing, Clouds offer capabilities for the high-availability of a wide range of systems. But it is argued that such systems will only attain acceptance by a larger audience of commercial end-users if binding Service Level Agreements (SLAs) are provided. In this paper, we discuss how to measure and use quality(More)
Infrastructure as a Service (IaaS) Clouds offer capabilities for the high-availability of a wide range of systems, from individual virtual machines to large-scale high performance computing (HPC) systems. But it is argued that the widespread uptake for such systems will only happen if Cloud providers, or brokers, are able to offer bilateral service level(More)
Infrastructure Clouds offer large scale resources for rent, which are typically shared with other users—unless you are willing to pay a premium for single tenancy (if available). There is no guarantee that your instances will run on separate hosts, and this can cause a range of issues when your instances are co-locating on the same host including: mutual(More)
The increasing number of public clouds, the large and varied range of VMs they offer, and the provider specific terminology used for describing performance characteristics, makes price/performance comparisons difficult. Large performance variation of identically priced instances can lead to clouds being described as 'unreliable' and 'unpredictable'. In this(More)
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