Like physical disk drives, virtual hard disks can become fragmented. Defragmenting disks rearranges files, programs, and unused space on the virtual hard disk so that programs run faster and files open more quickly. Defragmenting does not reclaim unused space on a virtual hard disk.

Defragmenting disks can take considerable time.


  • Verify that there is adequate free working space on the host system. For example, if the virtual hard disk is contained in a single file, there must be free space equal to the size of the virtual disk file. Other virtual hard disk configurations require less free space.
  • Verify that the virtual disk is not mapped or mounted. You cannot defragment a virtual disk while it is mapped or mounted.


  1. Run a disk defragmentation utility in the guest operating system.
  2. If disk space is not preallocated for the virtual hard disk, use the Workstation Pro defragmentation tool to defragment it.
    1. Power off the virtual machine.
    2. Select the virtual machine and select VM > Settings.
    3. On the Hardware tab, select Hard Disk.
    4. Select Utilities > Defragment.
    5. When the defragmentation process is finished, click OK.
  3. Run a disk defragmentation utility on the host system.