VC_FAULT_FATAL - A specified parameter was not correct: vm.ctkEnabled. Instant Clone Creation Error

Products

• VMware vCenter Server 6.0
• VMware vCenter Server 7.0

Issue/Introduction

• Outside factors can alter the value and introduce provisioning issues for Horizon Instant Clones.
• Cloning a virtual machine fails. 
• Instant Clone Provisioning fails with a Log Line entry similar to the below in a Connection Server debug file:
  https://kb.omnissa.com/s/article/1027744
  

  Cloning of VM "name" has failed: Fault type is VC_FAULT_FATAL - A specified parameter was not correct: vm.ctkEnabled.

Environment

VMware vCenter Server 6.x  
VMware vCenter Server 7.x

Cause

This is an expected behavior as a machine with this value set is not appropriate for usage as an Instant Clone.

Resolution

To resolve this issue, disable the vm.ctkEnabled parameter on the virtual machine.

Steps to Disable CBT (Change Block Tracking):

1. Power Off the Virtual Machine:

• Before making any changes, the virtual machine should be powered off to prevent data corruption or unexpected behaviors.

2. Access VM Settings:

• Right-click on the virtual machine in the VMware vSphere client or other management interface. Select Edit Settings.

3. Navigate to Configuration Parameters:

• Click on the Options tab.
• Under the Advanced section, select General.
• Click on Configuration Parameters, which will open the Configuration Parameters dialog.

4. Disable CBT:

• In the Configuration Parameters window, find the ctkEnabled parameter for the desired SCSI disk(s).
• Set the value of ctkEnabled to false. This disables Change Block Tracking on the specified disks.

5. Power On the Virtual Machine: Once you've applied the changes, power the VM back on.

Note:

• No Snapshots Before Enabling CBT:
  Ensure that no snapshots exist on the VM before enabling CBT. If snapshots were taken before enabling CBT, it may cause the QueryChangedDiskAreas API to not return accurate data. This is crucial for backup software and any other systems relying on CBT to track disk changes correctly.