Microsoft has explained how SkyDrive integration in Windows 8.1 Preview works. SkyDrive now uses placeholder files with only metadata and a large thumbnail preview for images to save space.
For example, a Pictures folder that is 5.6GB on SkyDrive may only take up 185MB on a tablet. These placeholder files can be browsed, searched and managed just like the full files, but they will not be fully downloaded until they are opened for editing.
Interested in learning more? See the Inside SkyDrive blog here.
