Identify BranchCache Deployment Goals

Updated: November 4, 2009

Applies To: Windows Server 2008 R2

Correctly identifying your BranchCache deployment goals is essential for the success of your BranchCache design project. Depending on the size of your organization and the level of involvement that you want to provide for the information technology (IT) staff in any partner organizations, form a project team that can clearly articulate real-world deployment issues in a vision statement. Make sure that the members of this team understand the direction in which your deployment project must move in order to reach your BranchCache deployment goals.

When you deploy BranchCache, you have a choice between the following:

• Deploy BranchCache in distributed cache mode to optimize wide area network performance for employees in branch offices with only client computers. Distributed cache mode does not require a server computer in each branch office; it also does not require that you purchase or deploy server certificates.

• Deploy BranchCache in hosted cache mode to optimize wide area network performance for employees in branch offices that contain server computers. When you deploy BranchCache in hosted cache mode, you must enroll a server certificate to hosted cache servers either by purchasing a certificate from a third party company, such as Verisign, or by deploying your own certification authority (CA) and enrolling server certificates to hosted cache servers.

• Deploy BranchCache in both distributed cache mode and hosted cache mode. When you deploy BranchCache in both modes, a hosted cache server is required at each branch office where you deploy hosted cache mode. A hosted cache server is not required, however, for branch offices where hosted cache mode is not deployed but distributed cache mode is deployed.

Hosted cache mode advantages

For various reasons, deploying BranchCache in hosted cache mode provides more wide area network (WAN) bandwidth savings than distributed cache mode, even when the branch office contains only a single subnet. In hosted cache mode, the hosted cache server is always on and the cached content is always available to clients that request the content.

In distributed cache mode, each client computer that downloads content from the main office content servers then acts as a client cache server, sharing the content with other client computers so that the other computers do not have to download the same content. But client computers power down, and portable computers might be removed from the branch office for undetermined periods of time, and when the computers are turned off or are absent from the office, the content that they cached is no longer available to other client computers. In this circumstance, the requesting client computer must obtain the content from the main office content servers, which means that the same content is downloaded more than once.

In addition, if you have subnets that contain many computers that use a wireless connection to the local area network (LAN), distributed cache mode performance suffers because transferring data over a wireless connection is typically slower than transferring data over a wired connection to the LAN. In this case, if you deploy hosted cache mode with a hosted cache server that has a wired connection to the LAN, BranchCache performance is improved.

Considerations for large branch offices

Because you can deploy only one hosted cache server per branch office, there are circumstances where it is a good idea to choose distributed cache mode rather than hosted cache mode. If the branch office contains more than 100 workstations and is a multiple subnet environment, a single hosted cache server might not be able to handle the workload for the entire branch. In this case, use distributed cache mode to distribute the caching services among many computers rather than just one.

Deployment goals

The following table lists the main tasks for articulating, refining, and subsequently documenting your BranchCache deployment goals.