Starting from Windows Server 2012 R2 Preview Edition, we can now perform online virtual hard disk resize while the virtual machine is running. That’s mean “No downtime”. Shutting down virtual machines is no longer required and this eliminates interruption to users accessing those virtual machines and helps reduce maintenance costs.
In order to perform online resize, you need to fulfill these requirements:
a) Use SCSI Controller.
If you view hard disk located in IDE controller, you cannot select the “Edit” option.
Meanwhile hard disk on SCSI Controller, you can select “Edit”
From there, you can easily expand or shrink virtual hard disk while the virtual machine is up and running.
Note:- Be careful when shrink hard disk as we do not want any lost files.
b) Use VHDX format
Example:- 10 GB VHDX
a) Expand from 10GB to 20GB
b) Shrink from 20GB to 15GB