What is Windows Image Boot (WIMBoot)?

Now that Windows 8.1 Update has been released, we want to talk about a new way that Windows 8.1 can be installed on Windows 8 logo-certified devices (since UEFI is a requirement) with smaller disks, e.g. devices with 16GB or 32GB SSDs or eMMC storage, while still ensuring that there is plenty of storage left for apps and data.

This new deployment option, called Windows Image Boot (or WIMBoot), takes a different approach than traditional Windows installations. Instead of extracting all the individual Windows files from an image (WIM) file, they remain compressed in the WIM. But from the user’s perspective, nothing looks any different: You still see a C: volume containing Windows, your apps, and all of your data.

This is supported with all SKUs of Windows 8.1, with the Windows 8.1 Update. (Remember, we’re not talking about a different version of Windows, just a different way of installing it.)

So how does this work? Effectively, you copy the WIM file into a separate “images” partition (just like you would for a recovery image), then use DISM to create pointer files from the standard C: operating system volume into the WIM file. These pointer files are completely transparent, and Windows knows how to boot the operating system (keeping all the files in the WIM) when configured in this setup. Behind the scenes, the disk looks something like this:

Wimboot

So let’s assume the WIM file (INSTALL.WIM) is around 3GB and you are using a 16GB SSD. In that configuration, you’ll still be left with over 12GB of free disk space (after subtracting out the size of the WIM and a little bit of additional “overhead”). And the same WIM file (which is read-only, never being changed in this process) can also be used as a recovery image, in case you want to reset the computer back to its original state.

How does that compare to a non-WIMBoot configuration? Well, on that same 16GB system there might be only 7GB free after installing Windows – and then only if you don’t set up a separate recovery image.

If you want to try this out yourself, the necessary process for setting this up on a computer are discussed in the ADK documentation. The basic steps:

Make sure you understand the requirements and pre-requisites for doing this, as discussed at http://technet.microsoft.com/en-us/library/dn621983.aspx. And recognize that at this point in time, existing deployment tools like WDS, MDT, and Configuration Manager do not include any native support for deploying Windows using WIMBoot, so this may be more of a manual process.

Expect to see new tablet devices in the coming months that come pre-configured using WIMboot.

Michael Niehaus, Senior Product Marketing Manager, Windows Commercial