As its name implies, the single-tiered logical architecture for one host locates all services onto a single machine. In general, such an architecture is best suited for enterprises that are:
Composed of 500 users or less
Not geographically distributed
Served by few administrators
Seeking an entry-level configuration
The following figure represents the single-tiered logical architecture for one host.
End-user client programs, such as Outlook and Messenger Express, form the User Tier. Tier 1 is a single machine running all services, including messaging, calendar, instant messaging, and directory. If you deploy Communications Express, the single machine is also running Web Server (or Application Server). The distinction of the single tier deployment is that end users communicate directly to the stores, and not through proxies or other agents.
The single-tiered logical architecture for one host requires a machine that provides sufficient CPU, memory, and storage. You should work with your Sun representative to determine the machine that best meets your organization’s needs for this type of deployment.
When implementing the single-tiered logical architecture for one host, you can position the deployment for growth into a multi-tiered architecture by assigning logical names to services. Such a configuration makes use of DNS mapping to direct users to the same front-end process (machine). If, in the future, you need to make changes to accommodate growth, such as splitting out services in a tiered fashion, users do not need to reconfigure their client applications. See Using Logical Service Names for more information.