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Extend and Allocate Windows VM Guest Disk Space

Author: Christian Screen | | August 26, 2010

The ideas is simple enough – I am running a VMWare image (Windows Server guest) and one of the disks (drives) that I have allocated space to falls short of what is really needed.  So, the first step is to use the VMWare Disk Manager to extend the drive.  That’s easy enough.  The next thing to do is to open the Windows disk manager and assign the unallocated partition spacing to an existing partition.  With that being said, this is great for Windows 2003/2008 and Windows 7 (Sorry, I don’t even count the worthlessness of Vista) but Windows XP requires a lot of extra steps that I won’t cover here but towards the bottom of this post I have a reference link to that solution.  If you are using any other Windows OS aside from XP then continue reading.

Using VMWare Disk Manger To Increase Disk Space

VMWare Disk Manager should come as part of your VMWare workstation or server application installation.  If not, just do a quick search for it and you should be able to get the download.  For easy access I’ve added the directory containing this application (ex: C:Program Files (x86)VMwareVMware Workstation) as part of my PATH environment variable so that I don’t have to type the full file paths into my command prompt when executing any routines with it.  I recommend that you do the same.

In order to increase disk space you’ll navigate to the VM Image folder in question via the command prompt.  You will be looking for the base vmdk file for whatever disk drive you will be extending.  In my case, I was extending a secondary drive on my VM guest, G:.  The additional VM Image drives are suffixed incrementally by a value of one so they are easily recognizable.  For example, if your base VMDK file is “myVM.vmdk” then an extra disk on the VM would be “myVM-0.vmdk”. Regardless of main drive or secondary drives, the process remains the same.

  1. Ensure that the VM Guest Image you are attempting to expand disk space for is OFF.
  2. Navigate to the directory containing the VMDK file in question.
  3. Enter the correct syntax for expanding the drive.  The syntax can be found with the VMWare Disk Manager examples and execute the command line.

F:> vmware-vdiskmanager -x35GB EPM_11x_2003Standardx86-0.vmdk


Allocating the Extended Disk Space from Windows

Once your use of the VMWare Disk Manger has succeeded – and if you have enough disk space on your host this command should succeed quickly (sub-minute), you will be ready to start the guest VM and allocate the newly added extra disk space.  Once your command line disk space extension succeeds, start up the VM Guest Image in question, then follow the steps below.

  1. Navigate to My Computer > Manage > Disk Manager
  2. Assess the Disk Manager and determine if the extra drive space was indeed successfully added (see drive G: in the image below has unallocated space).[simage=112,400,y,center]
  3. Right-Click on the existing drive space block in question and select “Extend Volume…”[simage=113,400,y,center]
  4. Follow the prompts.  The second prompt in the wizard automatically selects the unallocated disk space.  Just continue to click “Next” through the prompts until you are able to click “Finish”.[simage=114,400,y,center][simage=115,400,y,center]
  5. Confirm in Disk Manager that the space has been appended to the existing drive space by looking at the total space available for the drive in question.[simage=116,400,y,center][simage=117,400,y,center]
  6. Again verify the space by looking at the full computer disk space.[simage=118,400,y,center]
  7. You’re Done.


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