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So I have this NTFS HD drive and when I select all the files and directories in it's root (including hidden and system files) the total Size on disk is 460 GB, but when I look on the disk properties it says that the used space is 464 GB. There must be something wrong...

P.S.: I run Win XP Pro SP3, don't know if this matters. P.P.S: No, it's not about GiB vs GB.

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The MFT can get very large. E.g., small compressed files are stored there. – Anonymous Jan 21 '10 at 5:58
There are not much small files on that drive and I haven't activates NTFS compression, can you advice any tool to view the size of MTF, however? – user1393 Jan 21 '10 at 6:03
I know it isn't a utility specifically designed for MTF, but Diskeeper will show you the size of the MTF, amount used and allow you to change the size. – Scott McClenning Jan 21 '10 at 6:15
When you did the properties of all the directories and files in the root and got the 460GB, was that the "Size" or "Size on disk" amount. For example with NTFS formatted to it's default settings; if you open Notepad.exe make a text file with one character and save it. Then do the properties of the file it will say "Size: 1 byte" "Size on disk: 4.00KB") Could the amount of data be 460GB but the space taken on disk 464GB? – Scott McClenning Jan 21 '10 at 6:22
@Scott McClenning : read carefully, I already empathized that I was talking about Size on disk. – user1393 Jan 21 '10 at 6:35
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2 Answers

up vote 2 down vote accepted

There are lots of hiddens things that you cannot see in Windows Explorer. Your huge difference is most likely due to system restore, which puts backup copy of files into the "System Volume Information" folder.

To see everything clearly, I recommend WinHex. You can see the file size of MFT files (as shown in the picture), and go into the "System Volume Information" folder.

WinHex

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And by default, only the "SYSTEM" account has access to it, so even explorer as Administrator wouldn't be able to count it. – Anonymous Jan 21 '10 at 6:26
That's it! WinHex worked just great! And here is some info from Microsoft on how other users can access System Information Volume folder: support.microsoft.com/default.aspx?scid=kb;en-us;309531 – user1393 Jan 21 '10 at 7:45
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My first guess would be slack space (specially if you have lots of small files):

Quoted from wikipedia on fragmentation

For example, in many file systems, each file always starts at the beginning of a cluster, because this simplifies organization and makes it easier to grow files. Any space left over between the last byte of the file and the first byte of the next cluster is a form of internal fragmentation called file slack or slack space

My second guess is that you may have some errors on your filesystem, a check and repair may fix it.

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No, it's not the case of fragmentation, I think. There are about 20k files on the drive, I don't think fragmentation could eat so much space. And I already have run Windows check disk utility. I do think that you're right about errors on filesystem, however. But I don't know how to find them out and fix them. – user1393 Jan 21 '10 at 6:11
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