Server clustering is critical to the on-demand operating environment and, in particular, to the Web infrastructure. Server clustering can be used to help achieve continuous availability of Web sites. A consideration in architecting the Web infrastructure is the physical placement of the Web server, the J2EE Web container, and J2EE EJB container processes. It is possible to have each process run on its own physical machine or node, or grouped on one or two nodes. The scenarios described in this paper follow the practice of placing the Web server process on its own node and the Web container and the EJB container on a second node.