Virtual machines on vVols with CBT enabled might fail or restart after a failed migration.

Products

• VMware vSphere ESXi 8.0

Issue/Introduction

Virtual machines (VMs) residing on a vSphere Virtual Volumes (vVol) datastore may fail to run or restart unexpectedly following a migration attempt.

This issue specifically occurs when a vSphere vMotion task fails at a late stage in the migration process. After the failed migration, the VM enters a state where it cannot be powered on or restarted.

Environment

VMware ESXi 8.x

Cause

This issue is caused by a conflict in the state of the Virtual Machine when a vMotion operation fails near the end of the process. If Changed Block Tracking (CBT) is active on a disk within a vVol environment, the clean-up process after the failed migration may leave the VM in an invalid state, preventing it from running.

Resolution

This issue is resolved in VMware ESXi 8.0 Update 3h.

Workaround:

If you are unable to upgrade to ESXi 8.0 Update 3h immediately and are experiencing this issue, you can work around it by disabling Changed Block Tracking (CBT) on the affected Virtual Machines.

To disable CBT:

1. Power off the Virtual Machine.

2. Right-click the VM and click Edit Settings.

3. Click the VM Options tab.

4. Click Advanced and then click Edit Configuration.

5. Set the ctkEnabled parameter to false.

6. Click OK to save the changes and Power on the VM.

Additional Information

Changed Block Tracking (CBT): CBT is a feature used primarily by backup software to track disk sectors that have changed between backups.
Disabling CBT will force backup solutions to perform a full checksum calculation for the next backup cycle, which may increase backup times temporarily.