An Office Communications Server 2007 R2 deployment is based on one or more Front End Servers that provide IM, presence, and conferencing services and are connected to a Microsoft SQL Server database for storing user and conference information. Depending on your deployment, the database might reside on the same server.
Office Communications Server 2007 R2 offers two recommended configurations: the Standard Edition configuration and the consolidated Enterprise pool configuration. The Enterprise pool configuration consists of identical Front End Servers that are connected to a separate dedicated SQL Server Back-End Database. (In an Enterprise pool, the Back-End Database must be on a dedicated computer, separate from all Front End Servers.)
Standard Edition Configuration
A Standard Edition server hosts all necessary services on a single Front End Server. Because it requires a minimal hardware investment and minimal management overhead, the Standard Edition configuration is ideal for pilot and lab deployments, and for branch offices that do not have high availability and performance requirements. It is intended for deployments with fewer than 5,000 users either in total or at a particular location.
Enterprise Edition: Consolidated Configuration
Enterprise Edition: Consolidated Configuration is a pool configuration in which all server components are collocated on the pool’s Front End Servers (with the exception of the Back-End Database, which must reside on a separate dedicated computer). Consolidated configuration provides scalability and high availability and yet is easy to plan, deploy, and manage. The documentation for Office Communications Server 2007 R2 Enterprise Edition assumes the use of a consolidated configuration.