SLA Protection Models for Virtualized Data Centers

Enterprise services must satisfy strong requirements that are coded in agreements with customers, commonly called service level agreements (SLA). To satisfy SLAs in critical conditions, conventional data centers are often greatly over-dimensioned, wasting resources and raising service costs. Virtualized data centers (VDC) provide an opportunity to significantly reduce over-dimensioning, and so reduce service costs without negatively affecting service agreements, through dynamic adaptation. In this paper we discuss the problems involved in creating self adaptive enterprise services in virtualized data centers, and we investigate solution strategies. We envision a set of models that help adaptation controllers to identify suitable reactions to changes in service level agreement and environmental execution conditions. We introduce models at different abstraction levels, to support the evaluation of the impacts of adaptation actions on system and SLA. We explore the requirements and specify the characteristics of these models through a case study: a Video on Demand service delivered using VDCs.