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My computer says that I have a 74.4 GB drive. Of that 231 MB are free.

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TreeSize application states all my files take up 64.3 GB.

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Where is the missing 10 GB?

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Did you try SpaceSniffer from your last question+answer? It said it'll find things TreeSize will not. –  Wutnaut Jun 19 at 19:49
    
also run your program as administrator. Many folders will be denied access without it. –  Keltari Jun 19 at 20:23
    
@Keltari This program was run as Administrator. –  AngryHacker Jun 19 at 21:42
    
When you hold the mouse over "C:\" in TreeSize, what does it say for "size" vs. "allocated"? Note also that if you recently deleted some large files, the OS (or the filesystem) may not have updated its free space statistic (it is cached, not calculated every time). Same with the drive, particularly if there are filesystem errors (not serious, but e.g. minor stuff due to power loss, etc.). Run chkdsk on the drive, and also reboot the machine -- after that the free space counts will all be consistent and you can see if the issue persists. Until you do that, you're just guessing. –  Jason C Jun 19 at 23:18
    
See also blogs.msdn.com/b/ntdebugging/archive/2008/07/03/…, which describes not only what kinds of things take up hidden space, but ways to find out exactly how much is being taken up. –  Jason C Jun 19 at 23:20

5 Answers 5

I'd say that a lot of that missing 10GB is in the System Volume Information folder that your screenshot shows access denied.

The System Volume Information folder is where your System Restore snapshots are saved. Try disabling System Restore and see how much space that saves you.

You may also be losing space to the Offline Files feature, which stores information in C:\Windows\CSC -- another folder which TreeSize likely cannot see into.

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So I checked... System Protection was on, but it didn't take any space because there were no System Restore snapshots. I turned it off anyway. The Offline Files were on as well, but also were taking up zero space. I turned it off too. No change in disk space usage whatsoever. –  AngryHacker Jun 19 at 21:56

The reason for this could be a discrepancy between the size of a file and the amount of space it actually consumes on disk because of block sizes. Look at the properties of any file and I believe windows shows you both. I suspect explorer is listing the consumed space where as treesize is listing the file sizes.

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See here for a detailed explanation: howtogeek.com/180369/… –  Mark Jun 19 at 22:48

It seems to be a quirk of TreeSize.

You can hold the mouse over "C:\" in TreeSize, and you will see a field for "size" vs. "allocated", by the way, but this would not explain your difference (nor would other answers here regarding difference in allocated space) as TreeSize reports the allocated space (meaning that TreeSize would show a higher total than the sum of the file sizes, which is what you want).

There is a good general article about free space discrepancies in NTFS, although that primarily refers to discrepancies in what Explorer reports, and does not cover the difference between Explorer and TreeSize.

On my system (1TB drive with 4K clusters):

  • TreeSize reports 218,215.4 MB used
  • TreeSize reports 219,231.0 MB allocated (1GB wasted)
  • Explorer (drive properties) reports 259,068.5 MB used (reports cached free space value, shows ~40GB more than TreeSize)
  • Explorer (select all files => properties) reports 254,749.0 MB used (does actual calculation, leaves out hidden files, still shows ~35GB more than TreeSize)
  • chkdsk reports 258,166.9 MB used for files
  • chkdsk reports 354.8 MB used for indexes (TreeSize will not show this)
  • chkdsk reports 1055.66 MB used by the system (e.g. volume info TreeSize will not show this)
  • chkdsk reports 64.0 MB used by the NTFS log
  • chkdsk's total (259,641.4 MB) roughly matches Explorer's total (259,068.5 MB), TreeSize is the odd man out.
  • TuneUp Disk Space Explorer reports 252,794.88 MB (excludes system and hidden files, very close to Explorer)

Some discrepancies can be expected above due to the various techniques used to tally space, the list of files included, and especially hard drive activity that happened while I was performing the above (temporary file activity, search indexing, browser caching, etc.). So slight mismatches can be considered "close enough", but 35GB is not a slight mismatch.

As you can see, TreeSize is the odd one out. Explorer (both reported and tallied free space), chkdsk, TuneUp DSE, and df all reported consistent results. TreeSize is missing about 30-40GB of data.

That's not to say TreeSize is no good; I just wouldn't trust it to report all the data on the drive. That said, however, the data it is missing is likely data you would not want to or be able to delete anyways. TreeSize is still a perfectly good utility for locating trouble spots and data that can potentially be moved to other drives or deleted.

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It seems as if that program is not event taking into account the sizes of the page- or swap-file. Usually, they have a size in the dimensions of your RAM, so there could be the missing 10 GB.

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Most likely, you have hidden pagefile.sys and/or hiberfil.sys in root directory of drive C:. Try to enable showing hidden files in Windows Explorer and check what is their current size.

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