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Barracuda MSP Partner Toolkit

Change ID Is Invalid

Either a Hyper-V Standard or a Hyper-V Rapid Recovery backup has the following warning:

The Change ID of ___ is invalid. Therefore, the differential/incremental changes made on the VM could not be calculated.  Forcing a full backup.

This warning may appear repeatedly or it may occur once and be followed by a successful backup.  If the former, please follow the resolution steps provided in this article.

 

Explanation


For Hyper-V backups, Intronis tracks changes to virtual machines using our changed-block tracking (CBT) driver, called VHDTrack.  When the change ID of a virtual machine becomes invalid, the CBT driver is unable to capture all the changes to that virtual machine's disks and must force a full backup to guarantee restorability.

 

Resolution


In most cases, the Backup Agent will force a full backup and the change ID warning will go away.  If it does not, however, you can reset the CBT driver to force a full backup.

Note:  The steps outlined below will reset the CBT driver tracking changes on all virtual machines.  After resetting the CBT driver, a full backup will be forced for all virtual machines, not just the one(s) giving the change ID warning.

Before undertaking this procedure, make sure there are no Hyper-V backups running.

  1. Open an elevated command prompt and run the command:

    fltmc unload vhdtrack

  2. Expose hidden folders by going to Control Panel Folder Options View and checking the option for Show hidden files, folders, and drives.

  3. Go to the volume(s) where your Hyper-V host's virtual machine files are and delete the folder named $VHDTrack$Store$.

  4. Reload the VHDTrack driver by running the command:

    fltmc load vhdtrack

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