Skip to content

Enlarging a Windows 7 VM Disk

Let's say you setup a Windows 7 virtual machine, then by the time you've installed all the software on it, you're running low on disk space inside the virtual machine. ZFS makes it easy to increase the size of disk allocated to the Windows vm.

Caution: this action might cause Windows to require activation again.

  1. Shut down the virtual machine from within the Windows guest
  2. Find the name of the zvol that is being used as the root disk This will be zones/uuid-diskN for KVM or zones/uuid/diskN for bhyve.
  3. Check the current size with 'zfs get volsize'
    [root@00-19-99-b6-fa-12 ~]# zfs get volsize zones/708c73e3-48f2-4da5-a0a6-e161215a4215-disk0
NAME                                              PROPERTY  VALUE   SOURCE
zones/708c73e3-48f2-4da5-a0a6-e161215a4215-disk0  volsize   60G     local
[root@00-19-99-b6-fa-12 ~]#

In this case we can see that the disk is setup with a volume size of 60 gigabytes, which Windows takes as the size of the disk. 4. Set the volsize to some larger value (in this case 65 gigabytes):

    zfs set volsize=65g zones/708c73e3-48f2-4da5-a0a6-e161215a4215-disk0

  1. Start the virtual machine using vmadm

    vmadm start 708c73e3-48f2-4da5-a0a6-e161215a4215

  2. Connect to the virtual machine using either vnc or rdp (if you have already configured Windows for remote access).

  3. Login to the Windows guest using an account that has administrative privileges.
  4. Find the "Computer" icon in the start menu, right-click on it, and select Manage
  5. In the left-hand panel, click on Disk Management. In the lower right panel, you should see a partition table for "Disk0", showing your additional space as "Unallocated".
  6. Right-click on the "C:" volume (either in the upper or lower panel) and select Extend Volume.
  7. The 'Extend Volume' wizard will appear. Click Next.
  8. The default action is to add all the new space to your 'C:' partition. This is likely what you want, so click Next, and then click Finish.
  9. Close the 'Computer Management' window by clicking on the 'x'.

You should now see that your hard drive has expanded.