Stephen Dawson

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We propose a linear regression method and a maximum likelihood technique for estimating the service demands of requests based on measurement of their response times instead of their CPU utilization. Our approach does not require server instrumentation or sampling, thus simplifying the parameterization of performance models. The benefit of this approach is(More)
Resource allocation in the cloud is usually driven by performance predictions, such as estimates of the future incoming load to the servers or of the quality-of-service(QoS) offered by applications to end users. In this context, characterizing web workload fluctuations in an accurate way is fundamental to understand how to provision cloud resources under(More)
Analytic performance models are being increasingly used to support system runtime optimization. This paper considers the modelling features needed to predict the response time behaviour of an industrial enterprise resource planning (ERP) application, SAP ERP. A number of studies have reported modelling success with the application of basic product-form(More)
Key issues addressing appropriateness of triage decisions and the tools needed to support those decisions are identified in this article. The limitations of current approaches to appropriate utilization such as admission and continued-stay criteria, medical management models, bed control and bed management strategies, and rounding practices are discussed,(More)
We present a new technique for predicting the resource demand requirements of services implemented by multitier systems. Accurate demand estimates are essential to ensure the efficient provisioning of services in an increasingly service-oriented world. The demand estimation technique proposed in this paper has several advantages compared with(More)
We present a new technique for predicting the resource demand requirements of services implemented by multi-tier systems. Accurate demand estimates are essential to ensure the efficient provisioning of services in an increasingly service-oriented world. The demand estimation technique proposed in this paper has several advantages compared with(More)
This paper describes our joint research on performance engineering methods for services in shared resource utilities. The techniques support the automated sizing of a customized service instance and the automated creation of performance validation tests for the instance. The performance tests permit fine-grained control over inter-arrival time and service(More)
Performance analysis in traditional distributed computing systems has always been inherently complex given the combination and interplay of behaviours associated with various operational components such as application routines, operating systems, communication protocols, the network infrastructure, and CPU and storage hardware nodes. In Service Oriented(More)
Future NASA exploration missions to Mars, Europa, Titan, comets and asteroids are seeking to perform sampling, in-situ analysis and possibly return of material to Earth for further tests. One of the major limitations of conventional drills when sampling in low gravity environments is the need for high axial force and, as a result, heavy robotic mechanisms,(More)
This chapter covers the scientific background for the Service Level Module of the Unified Service Description Language (USDL). In addition to general service level concepts, we expand on two specific service level fields: security and trust. For that end we first review the state of the art in service level modeling, then we explain the design of the(More)