Storage vMotion fails with "Error encountered while unstunning the virtual machine for Storage vMotion." when CBT was disabled without the VM being powered off

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

• Storage vMotion is failed with error "Error encountered while unstunning the virtual machine for Storage vMotion."
  
  
• The vmware.log of the affected VM contains logs like below at the time of the error: 
  
  YYYY-MM-DDThh:mm:ss.sssZ Wa(03) worker-######## - SVMotion_CreateMirrorNodeAsFd: Couldn't lookup file /vmfs/volumes/DATASTORE_UUID/VM_NAME/VM_NAME-ctk.vmdk.
  YYYY-MM-DDThh:mm:ss.sssZ Wa(03) worker-######## - SVMotion_CreateMirrorNodeAsFd: Detected SvMotion failure during file /vmfs/volumes/DATASTORE_UUID/VM_NAME/VM_NAME-ctk.vmdk copy!
  YYYY-MM-DDThh:mm:ss.sssZ Wa(03) worker-######## - Disk_SVMotionCreateCBTMirror: Failed to create mirror node for migrating CBT file.
  YYYY-MM-DDThh:mm:ss.sssZ Wa(03) worker-######## - SVMotionPerDiskFileCreateMirror: SvMotion failed due to diskOpen event callback request failure for fileType 3
   
• The Change Block Tracking (CBT) was disabled on the VM before the Storage vMotion.
  The vmware.log of the affected VM contains logs like below before the issue occurres (This might be long before the Storage vMotion is initiated).
  
  YYYY-MM-DDThh:mm:ss.sssZ No(00) vmx XXXXXXXXXXXXXX ConfigDB: Unsetting "ctkEnabled"
  YYYY-MM-DDThh:mm:ss.sssZ No(00) vmx XXXXXXXXXXXXXX ConfigDB: Unsetting "scsi#:#.ctkEnabled"

Environment

vCenter Server 7.0
vCenter Server 8.0

ESXi 7.0
ESXi 8.0

Cause

When CBT is disabled without the VM being powered off, the VM has still reference to the VM_NAME-cbt.vmdk. This reference brings the error.

To disable CBT, the VM should be powered off before. For more details, see Changed Block Tracking (CBT) on virtual machines

Resolution

There are 2 options to remove the reference to the unused VM_NAME-ctk.vmdk.

- Take a snapshot of the VM, and delete the snapshot. This option does not require the VM to be stopped.
- Shutdown the Guest OS and then, power on the VM.

Note: There is no need to do both, just one is enough.