This topic recently came up with a customer:  as with CRM 4.0, CRM 2011 provides functionality to install separate roles or role groups to different servers in a deployment,  and these roles are made up of different server functionality, components, and services.  Installing roles to different servers allows the CRM deployment to scale out efficiently,  and in CRM 2011, installing and removing these roles is much easier than it was in CRM 4.0.

A question came up as to whether IIS is required if you are only installing the Back End Server group to a server.  IIS is of course required for a Full Server installation or a Front End Server installation,  however,  for a Back End server installation it is not required.  When performing the installation, the requirements check will show a green check mark for IIS even though it is not installed.  Then during the Back End server installation, IIS is not installed.  The following screen shots show that part of the installation:


The following is a list of the Serve Role Groups available for installation from the Dynamics CRM 2011 Implementation Guide.

Server Role Group Description Roles in this group
Full Server

Contains all roles from Front End Server, Back End Server, and Deployment Administration Server. By default, Microsoft Dynamics CRM Server Setup deploys the system as Full Server. In a Full Server deployment, server roles are not listed separately in Control Panel. To view the installed roles or make changes, right-click Microsoft Dynamics CRM 2011 Server, click Uninstall/Change, and then click Configure.

Front End Server

Enables the server roles for running client applications and applications developed with the Microsoft Dynamics CRM Software Development Kit.

Discovery Web Service, Organization Web Service, Web Application Server, Help Server
Back End Server

Includes the server roles that handle processing asynchronous events such as workflows, and custom plug-ins. These roles are usually not exposed to the Internet.

Asynchronous Service, Sandbox Processing Service
Deployment Administration Server Enables the server roles for components that are used to manage the Microsoft Dynamics CRM deployment either by using the methods described in the Microsoft Dynamics CRM 2011 Deployment Software Development Kit or the deployment tools. Deployment Web Service, Deployment Tools