Resize Online VM Hard Disk in Hyper-V Server 2012 R2 with the Easiest Way

December 30, 2014

This article is about how to resize online VM (virtual machine) hard disk in Hyper-V Windows Server 2012 R2 easily and fast. To complete this, we highly suggest you try AOMEI Partition Assistant Server Edition, which is an excellent partition management software especially for Windows Server OS.

About Windows Server 2012 R2 and its new function

Windows Server 2012 R2 is the latest Windows Server operating system developed by Microsoft company. One of the new features of Windows Server 2012 R2 is the ability to resize a virtual machines hard disk when it is running. In order to pull this off – all you need is a virtual machine with a .VHDX file attached to a SCSI controller (this functionality is not supported with .VHD files or IDE controllers). With this new feature, resizing online VM hard disk in Hyper-V in Windows 2012 R2 become much easier than before.

Advantages of this new function

When talking about the advantages, last sentence in above paragraph said it is simpler than before. How is the the specific? The resizing feature allows extending and shrinking a VM hard disk while the Virtual Machine is running. Thus, server administrators can avoid downtime to perform vhd maintenance tasks and there is no impact to end users. Users can still access VM and its volumes. This function reduces the maintenance costs associated with downtime of critical Virtual Machines. So more and more users update to Windows Server 2012 R2.

Resize online VM hard disk in Hyper-V 2012 r2

Now you understand the new feature, you may want to know how to realize it? It is easy! Let me show you operations step by step. Generally speaking, there are two main parts.

Part I - Resize VM hard drive

1.Locate the virtual hard disk that you want to resize.

2.Choose Expand or Shrink and click Next.

3.Input the new size that you want and click Next.

4.Click Finish.

Expand Virtual Hard Disk

Once you have finished this, the size of the virtual hard disk will be changed as you wish. However, it will not do anything with the partitioning on the virtual hard disk. So at this point in time you will have a bunch of extra, unused space at the end of the VM hard disk. To make use of it you need to login to the guest operating system and do something with it. That is Part II.

Part II - Resize partition on hard drive of the gust OS

When you open “Disk Management”, you will see the expanded size as an unallocated volume as shown in the following screenshot of the Virtual Machine, it is at the end of the disk.


To take advantage of this empty partition, with the Windows Server 2012 R2 built-in Disk Manager, you can do some basic operations, such as extending or shrinking H partition with the unallocated space, or creating a new partition on it.

Extend Volume

However, this article is about the easiest way. So I recommend you try a third-party partition tool - AOMEI Partition Assistant Server Edition, which is more professional than Windows Server Disk Manager and break many limitations of it. For example, with Windows disk management program, partition can’t be moved, while AOMEI Partition Assistant Server can do it freely. So when you want to extend system partition, you’d better try AOMEI Partition Assistant Server, because delete partition behind system partition is not reality. More functions of AOMEI Partition Assistant Server you can find from the below image.

AOMEI Partition Assistant Server

More about AOMEI Partition Assistant Server

Now that it supports the newest Windows Server 2012 R2, it also supports former Windows Server OSes, Windows Server 2008(R2), Windows Server 2003 as well as Windows 8.1/8/7/Vista/XP. AOMEI Partition Assistant has already get many reward from software markets. Its function and security are great. You can download to try it out.