Microsoft has brought a lot of information about Windows 8.1 at the TechEd 2013 conference, and one thing that is noteworthy is that Windows 8.1 is actually a feature-enhanced and compact version of Windows 8. There is no doubt that Windows 8.1 brings many improvements and new features.
More intriguing, Microsoft's senior marketing director Michael Niehaus said at the meeting that the space footprint of Windows 8,windows 8.1 was significantly lower than the development team removed some old components, temporary files, and improved NTFS compression technology. Thus freeing up more space for the user's computer.
Niehaus says the Windows 8.1 Preview installation requires 4GB of free space and does not cause Windows 8 recovery partitions to be overwritten.
Windows 8/rt upgrades to Windows 8.1 can be done with one click, all your settings, data, and applications will remain, but you will need to reinstall your application from the Win8.1 preview to the official version.