Middle Tier Architecture
The Middle Tier architecture is designed to support an environment with a large number of organizations with relatively fewer users per organization: up to 200 organizations with an average of 10 users per organization at an average 60 percent concurrency rate. In this design, a single CRM deployment group may be used to support the expected load.
Similar to the Entry Tier model, the Middle Tier architecture includes servers dedicated to CRM processes as well as servers running supporting infrastructure.
The following figure shows the architecture for a Middle Tier deployment, including supporting infrastructure.
Figure 3: Microsoft Dynamics CRM 2011 Architecture for Middle Tier Deployment