I tried the following today:
- started with 69.3 GB free
- ran Defraggler and then had 51.5 GB free
- used CCleaner to analyze Wipe Free Space - no result
- used CCleaner to wipe free space - it reported a few MB
- after that had 70.2 GB free
I don't know how a defragmentation works precisely, but my guess is that what happens is this:
during work Defraggler allocates free space on disk to be used for temporarily writing parts of files
when it finishes, this space is wiped, but it does not deallocate that space anymore. So, the space is free, but any task that reports the used space by just checking what is reported as used will treat this as used.
when you then run a task that does something with the files and free space on disk and recalculates the new results itself, that finds this space not used, so you then get the correct information. Tasks like delete system restore point, or wipe free space
So, my guess is that Defraggler needs to deallocate the extra space it used, and recalculate again in the end.
If there is anybody here who knows how this all works, I would like to hear if I am right (or wrong)