How does CBT/RCT work for Hyper-V 2019

[GabesVirtualWorld]

Hi
In a long running support case with Microsoft on a performance issue of 2019 discussed in this thread: microsoft-hyper-v-f25/windows-server-20 ... 62112.html

Microsoft Support asks me to do a test and disable CBT on the VEEAM Backup job and then see if performance gets better. However, I'm in doubt if that is a valid test, since (applying VMware CBT knowledge here) I would guess that by disabling CBT at the VEEAM Job, it only tells VEEAM to stop using CBT, but as these VMs have already been backupped a few times using CBT(RSC), I guess the tracking of changed blocks will continue, because other backup products could be using this CBT.

Is my assumption correct?

What is a way to "clear" CBT tracking from a VM? Is there a setting on the VM that I have to enable? Files to delete? Does the VM need a shutdown?

Does "Reset-HvVmChangeTracking" impact the running VM? Do I need to shutdown the VM first?

Regards
Gabrie

[HannesK]

Hello,

disabling CBT at the VEEAM Job

that's what I understood Microsoft asked for.

Disabling RCT itself is probably complicated according to my internet search skills. Just one of the results

Reset-HvVmChangeTracking can be applied to running VMs, but I'm not sure whether that satisfies the request of Microsoft request.

Best regards,
Hannes

[rold]

Just stop VM and remove remaining MRT/RCT files.

Reset-HvVmChangeTracking is for Veeam CBT filter not for native RCT.