Posted by Online expanding of a VHDX is only possible with:
VHDX files that are attached to a SCSI controller.
Note:
Generation 1 VMs Boot always from a IDE Hard Drive.
Generation 2 VMs Boot always from a SCSI Virtual Hard Drive.
The following Windows guest operating systems are supported as generation 2 virtual machines:
- Windows Server 2012 R2
- Windows Server 2012
- 64-bit versions of Windows 8.1
- 64-bit versions of Windows 8