Introducing Differentiated Availability in Cloud Computing SLAs

Cloud computing is the new trend in service delivery, and promises cost savings and agility for the customers. However, some challenges still remains to be solved before widespread use can be seen. This is especially relevant for enterprises, which currently lack the necessary assurance for moving their critical data and applications to the cloud. The cloud SLAs are simply not good enough. This paper focus on the availability attribute of a cloud SLA and argues that differentiated availability is needed for different customers requiring different services levels. Different techniques in use today for increasing the availability for stateless and stateful services in a virtualized system. The resulting availability is quantified using a two-level model, also taking into account the physical deployment of a service.