VDP 6.1 check if CBT is being used

We're having a customer doing a backup of a VM with a couple of TB's.

But looks like CBT is not being used, scanning the disks takes more than 24hours and we had to extend the backup window:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2109662

But after an initial backup, the next backup takes again more then 24hours but there are almost no changes on the disks.

looks like cbt is enabled. From the log: "scsi0:5.ctkEnabled = "TRUE"
"

Is there anyway to check if cbt is being used after an initial full backup.

Regards,

John