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Consolidating NTFS free space

Posted by jpluimers on 2017/12/29

For shrinking VM disk images, it’s important to consolidate NTFS free space towards the end of the this.

I’ve tried many tools, starting with defrag C: /X (which tries, but doesn’t give good results) and found out these steps give the best results:

  1. Perform an Ultradefrag full optimisation,
  2. Perform a MyDefrag Consolidate free space script on the drive.

If shrinking still fails then:

  1. Try the Ultradefrag at boot time
  2. Verify what kind of file(s) prevent shrinking: they show up in red after the MyDefrag session:
    1. Zoom in them (they can initially as small as 1 red pixel) by clicking on or near them, repeating the zoom long enough so you can hover over with the mouse and the lower part of the screen shows a filename like  where you cannot find much information about “$badclus:$bad:$data” but appear to be clusters marked as bad on NTFS level using something like chkdsk /B.
    2. If it was a bad sector like above, then try to resolve it with [WayBackntfsfix which ships with GParted live boot:
      1. boot a [WayBackGParted — Live CD/USB/PXE/HD drive,
      2. run GParted to see the drive path (for instance /dev/sda1)
      3. start a terminal
      4. run this command:
        ntfsfix -b /dev/sda1
        which will give output like this:

        Mounting volume... OK
        Processing of $MFT and $MFTMirr completed successfully.
        Checking the alternate boot sector... OK
        NTFS volume version is 3.1.
        Going to un-mark the bad clusters ($BadClus)... OK
        NTFS partition /dev/sda1 was processed successfully.
      5. boot back into Windows
      6. on an administrative command prompt run this for the affected drive letter:
        chkdsk D: /B
        (reboot if needed)
  3. Shrink the drive using diskmgmt.msc

If you still cannot shrink, then try [WayBack PerfectDisk by Raxco free trial.


MyDefrag (formerly named JkDefrag) is not maintained any more but the 4.3.1 version in the WayBack machine still works very well as the underlying defragmentation APIs in Windows haven’t changed.


For FAT32:

For GParted / ntfsfix:

PerfectDisk via:


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