Shut down the virtual machine and convert the chain of VHD-format differencing virtual hard disks to the VHDX format or merge ...

Shut down the virtual machine and convert the chain of VHD-format differencing virtual hard disks to the VHDX format or merge the chain to a fixed virtual hard disk. (The VHDX format has reliability mechanisms that help protect the disk from corruptions due to power failures.) However, do not convert the virtual hard disk if it is likely to be attached to an earlier release of Windows at some point. Windows releases earlier than Windows Server 2012 do not support the VHDX format.