When you prepare a parent image virtual machine for instant clones or linked clones, it is recommended that you disable scheduled defragmentation. Windows schedule weekly disk defragmentations by default. Defragmentation significantly increase the size of a clone's virtual disk and does not make disk access more efficient for instant clones or linked clones.

The clones share the parent image virtual machine's OS disk but each clone maintains changes to the file system in its own virtual disk. Any activity, including defragmentation, will increase the size of each clone's individual virtual disk and therefore increase storage consumption. As a best practice, defragment the parent image virtual machine before you take a snapshot and create the pool.

The following steps apply to Windows 7 and Windows 8. The steps might vary on different Windows operating systems.


  1. In vSphere Client, select the parent virtual machine and select Open Console.
  2. Log in as an administrator.
  3. Click Start and type defrag in the Search programs and files box.
  4. In the Programs pane, click Disk Defragmenter.
  5. In the Disk Defragmenter dialog box, click Defragment disk.
    The Disk Defragmenter consolidates defragmented files on the virtual machine's hard disk.
  6. In the Disk Defragmenter dialog box, click Configure schedule.
  7. Deselect Run on a schedule (recommended) and click OK.