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Resolved Huge disk usage discrepancies

Discussion in 'Windows 7' started by Sduibek, 2012/01/10.

  1. 2012/01/10
    Sduibek

    Sduibek Inactive Thread Starter

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    Picture says it all. I've had this happen on multiple drives of various formats - HDD, SSD, and SD/Flash USB. I believe it was NTFS in all cases.

    The is from alt-enter on the drive itself, versus select all then alt-enter from the root directory of the same drive. Please explain.

    Thank you.

    [​IMG]
     
    Sduibek,
    #1
  2. 2012/01/11
    TonyT

    TonyT SuperGeek Staff

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    No discrepancies in your images.

    Size = actual size of files in bytes.
    Size on disk = actual space on disk used by those files, the clusters used.

    NTFS uses 512 bytes per cluster. If a file is 450 bytes, the whole 512 cluster is used, the remainder is wasted space. This "wasted space" accounts for Size on disk being a larger figure than Size.
     
    TonyT,
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  4. 2012/01/11
    Sduibek

    Sduibek Inactive Thread Starter

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    No, that's not what i'm refering to. I'm aware of what you reference. I am saying the left image versus the right image. The actual BYTES are different in each, by a factor of almost four gigabytes. The 'drive info' says I have 151GB free, whereas based on the file info there's only 146GB free. Which is correct? Why would window says X free of X when the files say something totally different? That makes no sense at all.
     
    Sduibek,
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  5. 2012/01/11
    Steve R Jones

    Steve R Jones SuperGeek Staff

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    System Restore and the Recycle bin both reserve 10% to 12% Each of drive space which I don't believe gets counted in the pie chart pic.
     
    Steve R Jones,
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  6. 2012/01/12
    Arie

    Arie Administrator Administrator Staff

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    The other issue is that a "select all" on a drive doesn't get you the hidden & system files & directories.
     
    Arie,
    #5
  7. 2012/01/12
    Sduibek

    Sduibek Inactive Thread Starter

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    True on default settings, however, in this case I do have those displayed as well as the system files' checkbox, and furthermore that infobox is the one showing roughly 25% higher total size.

    This PC has both disabled.


    Essentially, when all files are selected, the Size before Size On Disk is 3583021250 bytes higher than the Size Used if you select the drive itself instead of any files. Why would roughly 3.5GB of data not show as being used on the drive, but show in Windows Explorer? Consider the small amount of data in question, that's roughly a 20% difference, which is a pretty big figure to be ghost data.
     
    Last edited: 2012/01/12
    Sduibek,
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  8. 2012/01/13
    Arie

    Arie Administrator Administrator Staff

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    If I elect to Show hidden files, folders, and drives and unselect Hide protected operating system files I get to a difference of 3.46GB
     

    Attached Files:

    Arie,
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  9. 2012/01/13
    Arie

    Arie Administrator Administrator Staff

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    Now the reason for the difference is:

    • There are some files and folders that you don't have access to, even as Administrator. System Volume Information is one such folder, Recovery another.
    • You can't directly see some items that take up space, like the MFT and USN Journal.
    • Files locked for exclusive use won't be counted either.
    • Explorer doesn't take NTFS Alternate Data Streams into account.

    Once I got access to System Volume Information I got another 2.3GB accounted for.

    To access System Volume Information, see How to gain access to the System Volume Information folder. Use the method listed below Windows XP Professional using the NTFS File System on a Workgroup or Standalone Computer and add your User account.
     

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    Arie,
    #8
  10. 2012/01/13
    Arie

    Arie Administrator Administrator Staff

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    Another thing to note is that the MFT file table can take up to 12.5% of the partitions size by default. You can use the defrag command from a command prompt to check the size of your MFT:

    At an elevated command prompt, type defrag c: -a -v

    Turns out my MFT is using 288.0MB
     
    Arie,
    #9
  11. 2012/01/14
    Sduibek

    Sduibek Inactive Thread Starter

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    All other things being equal, I think it's the WinSxS folder. Long story short, if I subtract the # of bytes in that folder from the total Select All bytes (left side of my picture), then compare to # of bytes listed for the drive selected (right side of picture), only about 200MB isn't accounted for. Which like you said could easily be the MFT.
     
    Sduibek,
    #10
  12. 2012/01/16
    Admin.

    Admin. Administrator Administrator Staff

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    If that answers your questions, please mark your thread as 'Resolved'.

     
    Admin.,
    #11

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