Used space does not match sum of all files

Question

I run Windows 10 in VirtualBox and get the following values regarding hard disk usage.

Used space: 12.2 GB.

Sum of all files: If I open Windows Explorer, select all files and choose properties, I get 17.8 GB on disk.

What's confusing is that used space is lower than the sum of all files. If anything, I would have expected it to be higher because the sum of all files depends on how Windows Explorer is configured regarding displaying system files. Plus all the NTFS stuff that is "invisible" in Explorer should show up in used space.

By the way, "Show hidden files, folders and drives" is selected and "Hide protected operating system files (Recommended)" is unchecked. If left at defaults, the sum of all files is about 1GB lower, which is OK and expected. But it's still way off compared to used space.

As a comparison, my Windows 7 host system has the following figures:

Used space: 97.1 GB
Sum of all files: 98.1GB (Size on disk: 98.6 GB)

With those numbers I can live. About 1% difference is nothing to worry about IMHO, but where do the almost 50% difference in Windows 10 come from?

Answer 1

Don't worry, you haven't lost any space. You'll be able to keep saving data until the volume is full - the drive's properties are telling the truth.

The discrepancy appears because Explorer double-counts files that appear under multiple names. Windows uses hardlinks for some system files, and to programs that don't account for that, they appear as completely separate full-size files.

A lot of files in \Windows\WinSxS are familiar/normal system files hardlinked to from other system folders. WinSxS can appear to be fairly large (>9GB on my Windows 8.1 machine), but most of the files in it consume no disk space by themselves. A difference of 5.5GB is entirely reasonable from WinSxS alone.

For more information about WinSxS, see Manage the Component Store.

To explore more about hardlinks (and other types of links), see Hardlinks and Junctions.

Answer 2

I would say this is result of virtual box not Windows 10. In my virtual drive I have similar disproportion. If I will check it through file system it uses 500 GB space, but if I check 100% of its space its 498 GB. That difference should be paths, aliases and other system information that is not counted at disk space view.

This difference depends on items count, not size. You have over 140k when I have just 18.