By Catherine / Last Updated December 30, 2014

The current situation

Nowadays, many users setup a virtual machine such as Windows Server 2008 (R2) or Windows Server 2012 (R2) running on Hyper-V. Why they like doing so? The most likely reason is saving money. Hyper-V can create virtual machines on x86-64 systems. What’s more, a host server running Hyper-V can be accessed remotely by multiple guest computers. Each guest computer could perform as if they are using the host server directly. people on the guest computers could run programs in the host server remotely, even though that program is not available on the guest computer.

However, as time goes by, users found that system partition had run out of space, delete files is impossible. Then question comes, how to extend Hyper-V guest system partition?


If you know more about Hyper-V, you should know the solve methods: extend the virtual hard disk using Hyper-V, then extend system partition inside the vhd. Notice that you must first completely shut down the virtual machine because you cannot extend a virtual hard disk that is associated with a running or saved stated virtual machine. If you expand a virtual hard disk that is associated with a virtual machine that has snapshots, these snapshots will be invalidated. If you need the snapshots, you’d better make sure you plan ahead of time, and create new snapshots after performing the expansion of the hard disk. After expanding the virtual hard disk there will be an empty space at the end of the virtual hard disk. You will try expand system partition using this unallocated space.

Part 1

At first, we highly suggest you make a backup of your VHD file after shutting the guest machine down.

Hyper-V VM

Secondly, open Hyper-V Manager and select the desired Hyper-V server, here, we take Windows Server 2008 as an example -> Select desired virtual machine in the center panel -> Select Edit Disk. Click Next to go, then browse and select the virtual disk on the Locate Disk page -> On the action page, please choose Expand.

Expand Virtual Disk

Type a new size and click finish.(Current and maximum sizes are provided in the window)

Input Disk Size

Thus Part 1 is almost finished. Start your VM and open computer Management - Disk Management, you will see there is an unallocated partition at the end of the disk because vhd size has been expanded. Now our task is extending system partition.

Part 2

We can’t directly extend system partition with Windows Server 2008 built- in Disk manager as shown in the following image: Extend Volume is gray and disabled.

Extend Volume Greyed Out

Since Windows Server disk manager unable to extend partition that has no unallocated space behind it. How to do? Is there any short cut? Yes, this is also the key point of this article - AOMEI Partition Assistant Server Edition.

AOMEI Partition Assistant is a powerful partition management software developed by AOMEI Technology. Its server edition is especially designed for Windows Server operating system, including Windows Server 2003, Windows Server 2008 (R2), Windows Server 2012 (R2), Windows SBS, etc. Next, let’s see how to use it to extend Windows Server system partition quickly.

Download, install and run. Right click C: drive or the unallocated volume, select “Merge”. In the pop-up window, check both partition C and the unallocated partition. Click “OK” will go back to the main screen.

Merge Unallocated Space

On the main interface, you can see some changes. System partition has been extended. There are three pending operations. At last, click “Apply” to commit these changes.

Click Apply

Only few steps, extending Hyper-V guest system partition succeed. AOMEI Partition Assistant Server is really an excellent and full scale software. It can do many partition optimization not only on Windows Server, but also on Windows PC OS. All in all, it is safe to use.