Hyper-V: Converting a VHD to a VHDX

On Windows Server 2012 there’s a new virtual hard disk format with the extension “VHDX”.

As the Virtual PC Guy states in his blog:

There are a number of advantages to this format:

• Support for greater than 2TB disks
• Better performance for dynamic and differencing disks
• Better handling of different disk sector sizes
• And more…

How to convert?

• Either manually (using Hyper-V Manager)
• or via PowerShell, using the Convert-VHD command

Will the size of my files change?

Yes, the new .VHDX files will probably be slightly larger.

Here’s an example of a sample conversion:

Description	VHD size (KB)	VHDX size (KB)	Change
System drive	22,316,615	22,581,248	(+ 1%)
Data drive	3,138,364	3,248,128	(+ 3%)