The continued success of the Apple iPad at eating into the laptop market has had me thinking about appliances—not the kind you find in your kitchen, but the kind that vendors such as Barracuda Networks and Azaleos sell. These appliances (for those of you who have been locked in a concrete bunker for the past few years) are essentially single-purpose servers that you install to provide a specific function on your network. The function, and hardware configuration, varies from vendor to vendor, but the basic idea is to deliver a service that requires a minimum of effort from the system administrator. The vast majority of appliances sold into the market are highly specialized. For example, if you're using a conventional hardware firewall, that's an appliance. So is the wireless router you have at home. So is your TiVo.

The whole idea of appliances seems like it would conflict with the direction that Microsoft Exchange Server (and now Lync) have taken: increasingly flexible, and complex, roles that can be combined or split onto separate machines. The idea behind appliances is to increase simplicity by clever packaging and configuration, and sometimes by adding vendor-specific utilities or customizations. For example, Barracuda's line of messaging-related products is based on open-source tools that Barracuda has extended and customized; Barracuda has added value to tools you could get for free by making them easier to configure and use, and by adding unique features.

Exchange Server has been largely immune to the appliance trend. Some functional areas, such as antispam and antivirus, have been successfully appliance-ized (a word I just made up) but Exchange itself hasn't. There are a number of reasons for this. The biggest reason is probably the simple fact that Exchange is designed to integrate with Active Directory (AD), Microsoft Outlook, SharePoint, and Office Communications Server (OCS)/Lync. This integration means you can't just stick a self-contained Exchange server into a rack and call it good—and as soon as you have to start integrating something with AD and other infrastructure components, you lose many of the theoretical time- and cost-savings that appliances offer.

Another reason is that Exchange designs aren't one-size-fits-all. For example, I have a customer with about 500 mailboxes that are geographically distributed between London and New York. This company has invested heavily in high availability. I have another customer of similar size whose users are all located in one building; their investments have been very different. Exchange works well for both customers—and many more besides—because of its flexibility. To some extent, flexibility is antithetical to the idea of a single-function appliance that does one thing easily and well.

Of course, another reason we haven't seen Exchange appliances is the advent of cloud-based services. Microsoft has invested heavily in designing Exchange 2010 so that the same code could run both locally and in the cloud, and cloud-based services—at least in theory—offer many of the same potential advantages as appliances: ease of installation, ease of use, and reduced maintenance costs.

Against this background, the recent announcement by HP of its new E5000 line of packaged Exchange solutions is particularly interesting. HP will be announcing more details of its new solutions soon, and I'll have more to say about them when that happens.

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