Resize a virtual hard disk for Hyper-v Server

Open the Hyper-v Manager, right-click Hyper-v Server and select Edit Disk; or in the Actions pane，select Edit Disk.

Click Next

Click Browse to select the virtual disk you want to change, then click Next.

Select the action you want to perform. You can do the following:

Compact: Reduces the size of a dynamically expanding or differencing disk by deleting empty space, while leaving the disk’s capacity unchanged.

Note: After the file is delete in the dynamic hard disk, the size of the hard disk file will not chang. For example，a dynamic hard disk file has 20GB, I copied a 10GB file to the hard disk, this moment the size of the hard disk file is 30GB, when I delete the 10GB file in this hard disk, the hard disk file size still 30GB. At this point you need to use Compact.

Convert: Creates a copy of the disk image file, enabling you to change the format (VHD or VHDX) or the type (fixed size or dynamically expanding) in the process.

Expand: Increases the capacity of the disk. 

Shrink: Reduces the capacity of the disk by deleting empty storage space from the file. The option only appears when there is unpartitioned space available at the end of the virtual disk.

Note: When the virtual machine is running only Expand and shrink options are available.

Merge: combine the data on the differencing disk and its parent disk to form a new file. The option only appear when you select a Differencing disk.

In this example, I chose Expand. Then click Next.

Type new virtual disk size in the New Size text box. Then click Next.

Click Finish

You can use the Optimize-VHD cmdlet on Windows PowerShell to compact a virtual hard disk file.

You can use the Convert-VHD cmdlet on Windows PowerShell to convert a virtual hard disk file. Form a VHD file to a VHDX file, from a fixed size file to a dynamic file or from a fixed size VHD file to a dynamic VHDX file.

You can use the Resize-VHD cmdlet on Windows PowerShell to expand or shrink a virtual hard disk size.

You can use the Merge-VHD cmdlet on Windows PowerShell to merge a differencing disk into its parent disk.