With Windows 8.1 Microsoft added compressed installation of Windows enabling OEMs to free up more space which is very important on small tablets that ship with small hard drives. In a post on the Windows Blog Microsoft have explained how they are going to achieve disk saving with Windows 10.
Windows 10 has improvements with the compression algorithms and no longer requires a recovery partition on the system as the Windows Refresh and Reset feature uses system files and not a special image. This should save a big chunk of disk space on new machines but I would be a little bit concerned that you are going to have to create your own recovery image to get back up and running if things really go wrong.
Recovery is lightweight and efficient
Without a separate recovery image, the Refresh and Reset functionalities will instead rebuild the operating system in place using runtime system files. Not only does this take up less disk space, it also means you will not have a lengthy list of operating system updates to reinstall after recovering your device.
Even though Windows no longer requires a separate recovery image, Windows can still recover a device from severe corruption. With Windows 10, you can create your own recovery media and back up the pristine state of the operating system and preinstalled software. If things go wrong and you are unable to refresh or reset your device successfully, you can boot the device using recovery media and reset to the prior pristine state.
One of the question we have been asking is will Windows 10 be able to upgrade tablets running a compressed version of Windows (WIMBOOT), these are special compressed images by device OEM and often have small disks which is why Microsoft haven’t released Windows 10 Technical Preview for the devices. In the post Microsoft don’t actually say how they are going to deliver the final version of Windows to these devices, they say they are evaluating the options for these devices.
In sum, WIMBOOT devices present a capacity challenge to the upgrade process and we are evaluating a couple of options for a safe and reliable upgrade path for those devices.
Have a read of Microsoft’s post for the technical details, it looks like we may have a little bit more disk space available once we are on Windows 10.