Proxmox VE VM Did Not Provide Valid CBT Data - Proprietary options

[Gavino]

In relation to this help page:

https://helpcenter.nakivo.com/Knowledge-Base/Content/Change-Tracking-Issues/Proxmox-VE-VM-Did-Not-Provide-Valid-CBT-Data.htm

The current solution says:

• Don't restart the VM image that is stored in the RAW or VMDK format non-persistent (limitation).

• Perform initial (full) backup/replication for the VM (this step creates a new dirty bitmap) and the next run runs CBT normally.

• Switch to the Proprietary method in case of a CBT failure:

  1. Run the backup with CBT by switching to use the Proprietary method (this step creates a new dirty bitmap).

  2. The next run shall use the CBT to run normally.

 

Well of course I have to restart some VMs from time to time, ether due to reasons with the VM (Windows updates, new Linux kernel / dist upgrades), or because I'm restarting the whole Proxmox node.  So that first point is is kinda funny but OK, moving on.

For the next point - well my initial backup was of course a full backup. I don't want to have to go change my Nakivo job settings for Change Tracking from "Use Proxmox VE CBT" to "No change tracking (always full)" after every time a VM gets rebooted. So not going to work for me.

That leaves me with what I see as the only sane (manageable) option which is the last one - switch to proprietary method in case of CBT failure, which thankfully creates a new Qemu Dirty Bitmap  (I had to google all about that... the equivalent to the VMware CBT file).

Diving into the Proxmox Change Tracking settings, we currently (as of 11.0.1) have the following set of choices:

	CBT Option	CBT Error Behaviour	CBT Error Behaviour Trigger Point
Proxmox Change Tracking	Use Proxmox VE CBT	Switch to proprietary method	·          Immediately ·          On the next retry ·          On the last retry
		Fail VM processing	·          Immediately ·          On the next retry ·          On the last retry
	Use proprietary method	n/a	n/a
	No change tracking (always full)	n/a	n/a

 

I have highlighted what I *think* is the right set of choices to remedy the issue of failing CBT, given the info in the URL I linked at the top of this post.

What I'm unsure about is the last column of "immediately / On the next retry / On the last retry".  I've gone with "Immediately" but is this the right choice? When do retries happen? I asked about this in another thread as well. Some info on this would be much appreciated.

Thank you,
Gavin O.

[Nicolas]

 

On 2/23/2025 at 5:12 AM, Gavino said:

When do retries happen?

It must be this one: https://helpcenter.nakivo.com/archive/10_4/Content/Settings/General/System-Settings.htm. If the job fails, it can make several more attempts.