For the Windows Server 8 Developer Preview, there are three main installation types: Full, Server Core, and Features on Demand. The Features on Demand option is new compared to Windows Server 2008 R2, and is made to provision a complete installation of Windows Server with the option for additional features available for installation remotely.
During an installation, selecting the new Features on Demand option will provide the basic features while additional roles and features can be added from a remote source. This is primarily a disk space-saving technique, and this option is shown in Figure A:
Features on Demand as an installation option.
The key difference with Features on Demand is that all of the capabilities of the server role can be run on this installation, but they don’t take up unnecessary disk space after the system is installed. Further, this will also reduce the surface area for Windows Updates, ongoing. I had a chance to talk to a distinguished engineer from Microsoft, Jeffrey Snover, about this very topic on a podcast, and the logic is that we can reduce the resources on the server yet increase the reliability. Giving this some thought, it makes perfect sense in the virtualized world and resource constrictive parameters that we deal with today.
On a Windows Server 8 system installed with the Features on Demand option, you can easily see how all of the features are removed with the DISM tool. The DISM is a deployment tool that can modify and report on Windows installations. See the following command:
Dism.exe /online /get-features /format:table
Running this on a default installation shows a number of features “Disabled with Payload Removed” listed for each feature, as shown in Figure B:
Listed features (click to enlarge)
This shows the feature inventory on a system, and in the case of Features on Demand installations, what is not consuming disk space for the features. A Windows Server 8 Core system takes around 5.5GB of disk space, a Features on Demand installation takes around 7.5GB of disk space, and a Full installation takes around 8.9GB of disk space. While a 1.4GB or so savings may not sound like a bunch, it would be significant across hundreds of virtual machines.
Does the Features on Demand installation option appeal to you? Share your comments below.