Q: What are the requirements to perform an online or hot resize of a virtual hard disk (VHD) in Windows Server 2012 R2 Hyper-V?
A: Windows Server 2012 R2 introduces the ability to dynamically resize a VHDX file connected to a running virtual machine (VM). This includes both extending a VHDX file and also shrinking a VHDX file, provided there's unpartitioned space within the VHDX equal to the amount the VHDX needs to be shrunk by.
If a VHDX is extended after the disk is refreshed within the VM, the new space will be visible and then new volumes can be created or extended volumes extended. The requirements to perform the online resize are as follows:
- It must be a VHDX file (not VHD).
- The VHDX must be connected to the SCSI bus and not the IDE bus.
- The VM can be Generation 1 or Generation 2.
- The guest OS can be Windows or Linux.
- You cannot online-resize a shared VHDX file.