Why & When to Use VHDX or VHD files with Hyper-V

Avatar Suman Kumar Updated On - 02 Aug 2018

In recent times, with the release of Windows Server 2012 various virtualization improvements occurred. Among these, one important improvement was the addition of the VHDX file format. It is very important to note that Windows Server 2012 supports the new format, and at the same time allows Hyper-V admins to make the proper usage of the old VHD format. However, the key question remains –

“When to Use VHDX or VHD files with Hyper-V?”

So, let us try to understand more about VHD vs. VHDX.

How VHD and VHDX differ?

In general, a virtual machine is an abstract computer. In fact, the entities that abstract a physical computer’s hard drive(s) are mere files, and for Hyper-V, these files are in the VHD/VHDX format. Now, if we try to make a comparison between VHD and VHDX, these are the major differences:

  • Compatibility: VHD is supported by 2008 and 2012 versions of Windows Server. But VHDX is supported by Windows Server 2012 only.
  • Capacity: With the old VHD file format, the storage limit is restricted to 2TB; but with the new VHDX format, it is 64TB.
  • Logical Sectors: The new VHDX format supports 4K logical sector size which is nice performance boost.
  • Data Protection: What is more special about the new VHDX format is that the protection it provides against file corruption from any other forms of unexpected IO failure (by tracking metadata).
  • Resizing: Live resizing is possible for VHDX files, whereas it is not possible for VHD files.

Now let’s look at different storage types with VHDX. Hyper-V allows you to create two primary hard disk storage types – fixed and dynamic. The great aspect about dynamic size is its requirement for minimum initial space. And the size expands proportionately as one uses the space. On other hand with the fixed storage type, the size for your storage is fixed. In terms of performance, fixed storage is efficient compared to the dynamic one.

Upgrade of VHD files to VHDX

An individual must Keep in mind that this new VHDX format cannot be used with Microsoft Server 2008/2008R2 and therefore in case you are preparing to place your virtual machine on a Microsoft Server 2008/2008R2 Hyper-V then make sure you keep your files in a VHD format. And Windows Server 2012 users are recommended to upgrade VHD files to VHDX in order to make the upmost utilization of the benefits the new format. One can convert VHD to VHDX format from Hyper – V Manager (Windows Server 2012) using the Edit Virtual Hard Disk Wizard (Actions > Edit Disk).