Adding a Legacy Virtual Disk to a Virtual Machine Downgrades It to a Legacy Virtual Machine

There are two solutions to this problem:

• (Best practice) If you do not want to use the legacy virtual disk on any legacy virtual machines:
  1. Add the legacy virtual disk to the virtual machine.
  2. After the reconfiguration task is completed, upgrade the virtual hardware of the virtual machine.
     Note that this changes the legacy disk. It is no longer usable by legacy virtual machines.
• If you need to keep your legacy disk usable by legacy virtual machines, you need to be aware that adding it to a modern virtual machine downgrades that virtual machine. Make sure you are not using any features that do not work on legacy virtual machines before adding the disk.

  Note: An invalid legacy virtual machine results if the downgraded virtual machine was already using features available only in modern virtual machines. If you already added a legacy disk that you do not wish to upgrade and an invalid virtual machine results, you cannot fix this in the graphical user interface. You cannot fix the problem by removing the legacy disk, because adding and removing virtual devices is not supported on legacy virtual machines. To fix this problem, you must recreate the virtual machine without the legacy disk.