Simplify Windows WAN Optimization With BranchCache

Using Windows Server 2008, Windows 7 and BranchCache, you can speed up file transfers for remote offices in your organization harnessing the spare storage capacity of hardware you've already got on hand.

 By Jabez Gan
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If your company has at least two sites, with the file server over at a remote site, have you ever thought about how to ensure users have access to their files in the shortest amount of time? If you are a seasoned IT administrator, you might be considering a brand new file server with distributed file server technologies (Distributed File Systems or DFS). But is there any better solution out there? BranchCache, available through Windows Server 2008 R2, is one possible answer.

With tight integration between its latest server and client software, Microsoft has made new enterprise-class features possible. This week, starting with BranchCache, I'll start off a series that introduces four features that can increase your company's business efficiency by using Windows Server 2008 R2 and Windows 7.

What is BranchCache?

BranchCache allows remote files to be cached on the local network, either on a Windows Server 2008 R2 server or Windows 7 clients. This allows faster access to files that have been accessed by users from the same location. It's a simple trick that can save lots of bandwidth, as this scenario demonstrates:

When a user (let's call him "Nick") wants to retrieve a file which is not available on the local file server/network, Nick's PC will need to download the file from the remote server through the WAN. Depending on file size and network connectivity, the download could take a few minutes or a few hours.

An extension to the above scenario: Let's assume that Nick and his colleagues will need to open the same file every morning. Without BranchCache, Nick and his colleagues' computers will download the same file individually, slowing WAN connectivity for everybody.

With BranchCache, once the file has been downloaded the local network's server or Nick's Windows 7 computer will cache it. For subsequent users who attempt to open the file from the remote server, their Windows 7 computers will automatically fetch the copy from the local network's server or Nick's Windows 7 computer.

How does BranchCache work?

BranchCache works in two modes: Hosted Cache, and Distributed Cache.

Hosted Cache

Similar to having file servers in the branch office, Hosted Cache allows files to be cached in any servers, as long as the servers are running Windows Server 2008 R2 configured with BranchCache. These servers do not necessary need to have File Services role installed for BranchCache to work. The servers at the branch office could be a web server, or a Read-Only Domain Controller for BranchCache to work. This will tremendously lower the cost when setting up small branches, as a dedicated file server is no longer needed.

Distributed Cache

Distributed Cache allows Windows client computers to cache the files which have been downloaded from the remote server, and allowing other local users to download from the Windows client computers cached files.

Distributed Cache mode relies on Windows 7 computers in the branch office to work. To use Distributed Cache mode, all participating computers in the branch must use either Windows 7 Enterprise or Ultimate (No, Windows 7 Professional will not work).

Microsoft recommends you use Distributed Cache only if your branch office has less than 50 Windows 7 client computers. Due to the architecture of Distributed Cache, the network will not be as efficient if more than 50 Windows 7 client computers are in use at the same time.

This article was originally published on Jul 31, 2010
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