Enabling Changed Block Tracking in vSphere 5.5 fails

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• The ctkEnabled flag does not remain set when you attempt to enable Changed Block Tracking on a virtual machine within the VMware vSphere Client.
  
  Note: For more information, see Changed Block Tracking (CBT) on virtual machines (1020128).
   
• After adding the ctkEnabled variables to the virtual machine's advanced parameters, the Reconfiguring virtual machine task completes successfully, but the variable is not applied to the virtual machine's .vmx file.

Environment

VMware vSphere ESXi 5.5
VMware vSphere Web Client 5.5.x
VMware vCenter Server 5.5.x

Resolution

This is a known issue in VMware ESXi 5.5.x, VMware vSphere Client 5.5 and the VMware vSphere Web Client 5.5.x.

Currently, there is no resolution.

To work around this issue, modify the virtual machine .vmx file to include the ctkEnabled flag.

 

To modify the virtual machine .vmx file through the command-line:

1. Power off the virtual machine you want to enable with Changed Block Tracking.
2. Log in to the ESXi host with the virtual machine as root.
3. Locate the virtual machine .vmx file.
4. Create a backup of the virtual machine's .vmx file using this command:
   
   cp virtualmachine.vmx virtualmachine.vmx.bak
   
    
5. Add this line the the virtual machine's .vmx file using a plain text editor:
   
   ctkEnabled = "true"
   
    
6. Save and close the file.
7. Power on the virtual machine.

 

 

Additional Information

For more information, see:

• Enabling or disabling Changed Block Tracking (CBT) on virtual machines
• Resetting Changed Block Tracking for VMware vSphere virtual machines