I'm on Windows 10 and using Backup and Restore. I'm not storing any system Images, but instead backing up files and folders. Following instructions on another post here, I completely wiped my earlier Backup and Restore settings in the registry and deleted all the data.
I attempted to backup my entire C-drive (150GB) Artwork and Source Code (4GB - 20k files) My Music Library (416GB - 55k files)
The destination drive had 1.36TB of free space. I would have expected it to use roughly 600GB of space (580 plus some overhead). The backup errored out 13 hours after it started at 57% done, completely using all 1.36TB.
What's going on here? Every file could have been written twice in the space I had, but it didn't even come close to backing it all up.