Towards Continuous Availability of Internet Services through Availability Domains

The increasing number of Internet users has caused a dramatic increase in electronic commerce. This growth is outpacing technologies for dependability causing traditional views of high availability to come under question. In particular, Internet failures are a phenomenon external to the owner of a commerce site that must be dealt with, and therefore, geographically distributed servers are a basic availability requirement for e-commerce sites. Geographic distribution provides an opportunity to view users in different roles based on those distributed components they must access. This paper presents an approach based on partitioning on-line function into domains, each of which provides service to users in a specific role. Coordination between domains is eliminated as much as possible by exploiting application-specific knowledge. Once partitioned, availability techniques may be applied to each domain in-dependently. We argue such an approach is necessary to deal with the geographic distribution of system components imposed by the nature of the Internet and maps well onto real e-commerce deployments.