Warning: "Some hard drive properties cannot be modified while the virtual machine is powered on"

Products

• VMware Cloud Director

Issue/Introduction

• Unable to extend the capacity of a virtual machine's hard disk (such as a primary boot drive) from the VMware Cloud Director UI.
• The disk size value field appears greyed out and is completely uneditable.
• Unable to extend Disk nor perform snapshot operation from VCD/vCenter. It fails with error:
  
  "The hard drives of the virtual machine "##" may not be modified, once created"
  
  
• Another possible error displayed in VMware Cloud Director UI:
  
  "Fast-provisioned hard drives and hard drives part of a VM snapshot cannot be resized"

Environment

VMware Cloud Director 10.x 

VMware vCenter Server 8.x

Cause

This issue can occur when the virtual machine is currently powered on and is deployed using fast-provisioning. VMware Cloud Director restricts modifying the base disk size while a virtual machine is actively running. Furthermore, fast-provisioned VMs utilize a delta-disk chain architecture that inherently relies on a parent disk. If the VM chain length is 2 or greater, modifying the base disk size is restricted by design until the VM is fully consolidated into a flat, full clone.

Resolution

Warning: Only manage the VMs from VCD and do NOT perform a Consolidate in the vSphere UI.
The Consolidate Disks action in VCD is a Promote Disks operation in vCenter, which is different from the Consolidate action in vCenter.
 
Consolidate the Fast Provisioned VM from Cloud Director so that it no longer depends on the Parent Disk

1. Log in to the VMware Cloud Director UI using administrator credentials.
2. Click the affected virtual machine to open its details and view the General tab.
3. Scroll down to the bottom of the General tab and verify that the Chain Length is 2 or greater.
4. Power off the virtual machine All Actions > Power > Power Off.
5. Ensure the VM's status shows as fully powered off in the VCD UI.
6. Click the All Actions and select Consolidate Disks.
7. Wait for the consolidation task to succeed.
8. Verify completion by checking that the Chain Length on the General tab has successfully dropped to 1.
9. Navigate to the Hardware > Hard Disks menu for the VM (while it remains powered off) and click Edit.
10. The Size field will no longer be greyed out, allowing you to increase the capacity and click Save.