Source: http://www.lazywinadmin.com/2013/01/enabling-change-block-tracking-cbt-on.html+

How to Enable CBT on your VM ? (PowerShell/PowerCli)

You can do the following even if your VM is Powered ON.

# Check and Add the PowerCli Snaping if not already present
if(-not(Get-PSSnapin -Registered -Name "VMware.VimAutomation.Core"){
    Add-PSSnapin -Name VMware.VimAutomation.Core}

# Connect to my Vcenter
Connect-VIServer -Server vcenter.fx.lab

#Here is aRunning the script on TESTSERVER04 to enable CBT
$vmtest = Get-vm TESTSERVER04 | get-view
$vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec
$vmConfigSpec.changeTrackingEnabled = $true
$vmtest.reconfigVM($vmConfigSpec)

How to Apply this CBT configuration ?

Once you enable CBT, the VM must go through a stun-unstun cycle (power on, resume after suspend, migrate, or snapshot create/delete/revert) before the reconfiguration takes effect.

How to Check if CBT is enabled on your VM (PowerShell/PowerCli)

# Check if your VM has (Change Block Tracking) enabled or not
(Get-VM -Name TESTSERVER04).ExtensionData.Config.ChangeTrackingEnabled

# Find VMs where CBT (Change Block Tracking) is Enabled
Get-VM| Where-Object{$_.ExtensionData.Config.ChangeTrackingEnabled -eq $true}