Blog Archives

BranchCache

This is the second part of a feature comparison series where I look at the differences between Microsoft Windows 7 Professional and Enterprise editions. For the full list of features, see the first post.

In this post I’ll review the usage scenarios and explore the benefits and caveats of BranchCache, and hopefully help you decide if it makes a compelling case for the extra cost of the Enterprise license.

As the name suggests, BranchCache enables caching on Windows 7 systems and it is aimed at branch offices. This is not to say it will only work in branches; it will work on any high latency network. BranchCache works with network requests made over SMB, HTTP or BITS, therefore websites, Windows file shares, WSUS and System Centre content can be cached. Once you enable BranchCache, Windows 7 clients will be able to retrieve cached copies of data either from a specified cache location (Hosted mode) or from Windows 7 peers (Distributed mode), rather than over the WAN. This will reduce the time it takes to retrieve files, is transparent to users and will reduce your WAN utilisation.

Since distributed mode is effectively peer-to-peer caching it is ideal for sites where it is not viable to host any servers. In this mode a Windows 7 system will first check with its peers whether a desired file is cached by any of them. If it isn’t, the file will be retrieved as normal and cached by the requesting client. The next time the file is requested by a client the file will be retrieved from the peer(s) where it is cached, but only if the file stored on the content server has not changed since it was cached.  Distributed caching is simple to enable and doesn’t require additional hardware or software investment on the client. The price you pay for all this “free” caching goodness starts with the extra cost of the Enterprise license, and the disk space (5% by default) and processing power that peer-to-peer caching will consume on you Windows 7 clients. but the real cost lies in the fact that all of the file/web/content servers at head office need to be running Windows Server 2008 R2 to play nice with your BranchCache clients. Not a problem if your servers are already up to date, but possibly a deal breaker otherwise.

This brings us to Hosted mode caching. Hosted mode is well suited to environments where resources are accessed via slow networks, but where it isn’t viable to set up and maintain local replicas of your content servers. In this scenario the cached data is held on a designated server. It can be a dedicated server or a server with available disk/processor capacity, but it does have to be a Windows Server 2008 R2 system. As with distributed caching, the servers that store the original content need to be running R2. Client setup is via group policy again and setting up the cache host requires the File Server role to be installed along with its BranchCache sub-component. The caching mechanism is similar also, except that clients refer to the central host instead of referring to peers when looking for cached data.

I would recommend Hosted caching only if Distributed caching does not provide adequate responsiveness or creates too much peer-to-peer workload on Windows 7 clients. Your results will vary so it’s worth monitoring performance in a small test group before and after implementing this feature, but according to an internal case study, “Microsoft IT significantly improved service availability while maintaining network traffic encryption including HTTPS and IPsec and reducing WAN usage and server demand”, and “Using BranchCache, Microsoft IT expects to save money while increasing branch user productivity.”

For a more detailed overview of BranchCache review this TechNet article, or download the Deployment Guide for a step by step walk through.

The next article in this series deals with Bitlocker and Bitlocker To Go.

Advertisements