Windows Server AppFabric Web Farm Guide

Windows Server AppFabric is an extension to Internet Information Services (IIS) 7.0 using the Windows Process Activation service (WAS). Windows Server AppFabric hosting and management delivers improved hosting and management of .NET Framework 4 Windows Communication Foundation (WCF) and Windows Workflow (WF) services.  AppFabric hosting and management provides support for improved management, deployment, and simplified configuration of these services.  Windows Server AppFabric caching offers a high-speed in-memory cache to improve scalability of .NET Framework and ASP.NET applications. For more information about the hosting, management, and caching capabilities of Windows Server AppFabric, see Windows Server AppFabric.

Within a small AppFabric installation or within a development environment, having a single AppFabric server is sufficient. In this configuration the SQL Server instance may even be on the same server as AppFabric, and users’ processing needs can be met.   However, in a larger production environment, a Web farm using multiple AppFabric servers is recommended to handle increased user load. Load balancing distributes incoming requests so that the processing of incoming messages is spread across multiple servers. With a Web farm of AppFabric servers, you can implement load-balancing solutions using a hardware or software element on a common front-end dispatcher.  For example, you could use the software option of Network Load Balancing Services (NLBS) that comes with Windows Server 2008 Enterprise Edition.   For a technical overview of NLBS, see Network Load Balancing Technical Overview. For more information about step-by-step configuration of NLBS, see Network Load Balancing Step-by-Step Guide.
Web farms not only increase performance by reducing the load on each server, but also increase availability. If one server in the Web farm is disabled (for example, taken offline for maintenance), other servers in the Web farm take over, so users are never aware of the offline server. Servers within a Web farm share a pool of resources and minimize chances for performance bottlenecks due to resource contention.  For more information about high performance, high availability, and load balancing in Windows Server 2008, see High Availability.
The focus of this document is to assist you in properly installing and configuring Windows Server AppFabric on an existing IIS Web farm. It assumes that you have already configured a farm of IIS Web servers, have a load balancing cluster of servers in place, and are preparing to install and configure Windows Server AppFabric hosting and management on each of the servers.