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 exploting application-specific knowledge. Once partitioned, availability techniques may be applied to each domain independently. 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.