Empty changeId in disk snapshot

[BooYan]

Every snapshot I create always result in an empty changeId. The CBT is enabled. I have checke

Limitations on Changed Block Tracking

Changed block tracking does not work if the virtual hardware version is 6 or earlier, in physical compatibility RDM mode, or when the virtual disk is attached to a shared virtual SCSI bus. ESXi 3.5 supported only up to virtual hardware version 4.

Changed block tracking can be enabled on virtual machines that have disks like these, but when queried for their change ID, these disks always return an empty string. So if you have a virtual machine with a regular system disk and a pass-through RDM as a data disk, you can track changes only on the system disk.

The compatibility of my vm is ESXi 6.5 and later (VM version 13). I do not use RDM mod and SCSI bus is not sharing. I have no idea why change id is empty. Any Help is very appreciated.

ps: I use govmomi to get changeId in device info.

[SupreetK · Accepted solution]

Can you refer to the below link and check what is the status of CBT (true or false) and the value of 'Change ID' in the MOB page for the VM in question?

Backup and Change Rate, Part 2: Querying Change Rate - Veeam Hub​

Cheers,

Supreet

[BooYan]

I found it according to your link. The reason I found an empty changeId previosly is that I use current vm configure to retrieve changeId instead of vm configure in a snapshot. Thanks a lot.