In moving from the logical architecture to a deployment architecture, quality-of-service requirements become paramount. For example, protected subnets and firewalls might be used to create a security barrier to back-end data. Availability and scalability requirements might be met for many components by deploying them on multiple computers and using load balancers to distribute requests among the replicated components.
However, where more demanding availability requirements apply and where large amounts of disk storage is involved, other availability solutions are more appropriate. For example, Sun Cluster can be used for the Messaging Server store and multimaster replication can be used for Directory Server.
For more information about Java ES solution deployment design, see the Sun Java Enterprise System 2005Q4 Deployment Planning Guide.