Upgrading OS in VM without causing a full backup

[PaulNSW]

I'll be updating some old 2008 file server VMs to 2016 in the next few weeks.
At the moment, the OS is on one vdisk, with the data on separate vdisk(s).

The last time I upgraded a file server VM from 2008 to 2016, I created a new VM, installed 2016, then disconnected the disks from the old 2008 vm, and reconnected them to the 2016 vm. The 2016 vm then gets the same name and IP address, but as it has a new VMGUID(?) Veeam sees it as a completely new VM, and performs a full backup.

Is there a way to get Veeam to see a new VM as the old VM, and only take a backup of the changed OS disk? Maybe it's just easier to wipe the existing OS disk and reinstall Windows 2016?

[Gostev]

Veeam tracks VMs using moRef VM identifier in vSphere API. If you create a new VM, it will get new moRef assigned by vCenter.

[Regnor]

You could prepare the new 2016 server in a separate VM and then switch the system disk with your existing 2008 VM.