When power on CBT enabled virtual machine, Guest OS boot took long time

Products

• VMware vSphere ESXi

Issue/Introduction

A CBT-enabled virtual machine may take an unexpectedly long time to open the disk during boot due to reinitialization of the ctk file.

• vm.vmx file
  

  ctkEnabled = "True"

• vmware.log
  

  [timestamp] In(05) vmx - DISKLIB-CTK   : Change tracking invalid; reinitializing.
  
  ...
  
  [timestamp] In(05) vmx - DISK: Opening disks took ######## ms.

Cause

The following conditions cause the ctk file to be reinitialized when the virtual machine is powered on.

1. Vmdk descriptor file was manually changed to point a wrong ctk file.
2. The vmx process was crashed before.
3. The ctk file was copied from somewhere that its disk is on open state causing the dirty flag of the ctk file is not cleaned up. It is a user error.

Resolution

The behaivior is expected.
Reinitializing ctk file took long time.
Leave the virtual machine powered on and wait until reinitialization is complete.