This specification describes the VHDX virtual hard disk format that provides a disk-in-a-file abstraction. This specification assumes that you are familiar with hard disk technologies, including how hard disks interface with the operating system or a virtual machine and understand how data is accessed and laid out on the physical medium. This specification is released under the Microsoft Open Source Promise (OSP) initiative to help guide development of VHDX virtual hard disk format implementations that are compatible with those provided by Microsoft.

This specification describes the VHDX virtual hard disk format that provides a disk-in-a-file abstraction. This specification assumes that you are familiar with hard disk technologies, including how hard disks interface with the operating system or a virtual machine and understand how data is accessed and laid out on the physical medium. This specification is released under the Microsoft Open Source Promise (OSP) initiative to help guide development of VHDX virtual hard disk format implementations that are compatible with those provided by Microsoft.

But what if you have a collection of VHD files? Luckily, converting to a VHDX format is simple (though potentially time consuming). To do this – all you need to do is:

Open the Hyper-V Manager
Select Edit Disk… from the action pane (or from the Action menu)
Click Next to get past the introduction page of the Edit Virtual Disk Wizard
Enter the name and location of your existing VHD file on the Location page and click Next
On the Choose Action page select Convert and then click Next
On the Choose Disk Format page select VHDX and click Next