Orange County, Tustin, CA 92780

How to Expand VMware Disk Size for Windows VMs

 As a System Administrator or System Engineer, one of the most frequent requests you'll receive is to expand the disk size on virtual Windows Servers and Windows Desktops. Most of the time, it's straightforward: 1) make sure you have enough space on the SAN, 2)

add the requested space on the VM, 3) use Disk Manager to rescan the disk to see the newly added space, 4) and expand the drive to its full size. It's easy if the newly added space is next to the partition you wish to expand. It's not easy if the adjacent space is some other partition with data. 

Here's what I'm talking about when added space is not contiguous. 

Windows Disk Management

What are your options if you see the above? The C drive partition that needs to be expanded is next to the Recovery Partition instead of the 20 GB Unallocated space. 

You could rebuild windows, you can use dynamics disk, and quite possibly other solutions, but there is an easier option. 

The Fix

Before making any changes, especially in a production environment, take a snapshot, a backup, or a SAN snapshot. Always give yourself a way out in case you make mistakes.

 We'll be using GParted to move partitions and then add the space to the portion that needs it.

  1. Expand the disk size on the VMware side. The OS will see it, but you won't be able to use it just yet.
  2. Take a snapshot of the VM or take a backup. I'm very cautious, so I do both. Remember to expand the disk size first, then take a snapshot. 
  3. Download Gparted using the most appropriate option for you. In our case, we used the amd64 ISO image.
  4. Launch the VMware Remote Console (not Web Console). This is needed for the next step.
  5. Within the menu, go to VMRC, Removable Devices, CD/DVD Drive 1, and choose Connect to Disk Image File (iso) to connect the ISO file downloaded previously.
    VMware Connect ISO file
  6. Make sure the VM is set to boot from the virtual CD-ROM. From the VMware vSphere Client, right-click the VM and go to Edit Settings...
    edit settings vmware vm
  7. Go to VM Options, Boot Options, and check the box to Force EFI Setup (Or Force BIOS setup, depending on how you set up your VM).
    Force EFI Setup or Bios Setup
  8. [IF NEEDED] If the VM uses the VMware Paravirtual SCSI (PVSCSI) controller, you'll need to power down the VM and change the SCSI controller to LSI Logic SAS for GParted to recognize the partitions correctly. Don't forget to change it back once the expansion is complete as the very last step.
  9. Power or Reboot the VM depending on what state you have it in to boot from the virtual CD-ROM.
    VMware - VM Boot Manager - Boot from CD-ROM
  10. Run GParted with all the defaults until you get to the main GUI by hitting Enter for all options. GParted will launch, showing you all your partitions.
  11.  Select the System Recovery Partition by clicking on it, then click on the Resize/Move button. You can select it either via the visual representation of it toward the top or the table below.
    GParted Selected System Recovery Partition
  12. Click and drag the partition from the left side of the screen to the right side to move the partition to the end of the disk. Do not drag the arrows, but click on the center where you see the yellow.
    gparted move partition
  13. You'll get a warning stating the following: "Moving a partition might cause your operating system to fail to boot." Click OK.
  14. Notice the partition is ready to be committed to its new location and is shown toward the end of the disk now. Click the green check box to Apply All Operations. This may take a few minutes.
    gparted moved partition
  15. Your main partition is now next to the empty space so that it may be expanded. You can expand it here or within Windows. Since we're here, we'll continue to use GParted.
  16. Select your main partition and click on the Resize button.
    gparted move primary partition
  17. Click and drag the black arrow all the way to the right to expand the partition and click on the Resize/Move button.
    gparted resize primary partition
  18. Notice that all the unallocated space is gone. Click the green arrow to commit your change. This may take a few minutes.
    gparted commit resize of partition
  19. You'll get a window with a message saying, "Are you sure you want to apply the pending operations?" Click Apply. This will take a few minutes.
  20. You're good to close GParted and shutdown the VM.
  21. [IF NEEDED] Revert the SCSI controller to VMware Paravirtual SCSI controller if you changed it in the earlier step.
  22.  Sometimes, when you boot to Windows, the OS will ask for a Check Disk of the C drive. Let it run to make sure any issues are corrected.


We used this particular solution quite a bit when we deployed Windows 10 VDI and realized the default installation created system partitions toward the end of the drive instead of the beginning. It was not until months later, when someone sent in a service desk ticket, that we realized this was an issue, but by then, we had already deployed dozens of VMs. While we could reissue a new VM, we opted to keep the VMs and deploy a new template that did not have this issue. Newly deployed VMs would not have this issue.

Sometimes when creating your golden images, things get missed. Since this is not typically an issue, we didn't check it. Check your templates; you may find you have this issue. 

Byron Zepeda

Byron Zepeda is a Senior Systems Engineer in Orange County, California, working with VMware vSphere, Citrix Virtual Apps, backups, and storage. As cloud technologies and automation become first-class citizens within IT organizations, he desires to share everything he learns and pass it on to others.