Incremental Backup Converts to Verify Backup or the Backup Size Increases in Hyper-V

Valid on Hyper-V VM

Symptom

I have performed an incremental change in a Hyper-V virtual machine. When I perform an incremental backup, the entire virtual machine is backed up instead of backing up only the changed data.
I have a proxy server with Arcserve UDP Version 6.0 that backs up a virtual machine from one Hyper-V host (example HOST1). I have another proxy server with an older version of Arcserve UDP that backs up a virtual machine from the same Hyper-V host (HOST1). In such cases, the CBT is inactive and the Incremental jobs do not run. The Incremental backup converts to the Verify backup.

Solution

The root causes of above symptoms can be one of the following reasons:

The loss of change block tracking (CBT) data. The following circumstances will result in CBT data loss:
- The Hyper-V host crashes or is powered off abnormally.
- The CBT service is stopped or the service abnormally quits.
- The CBT service did not complete its work while the Hyper-V host was shutting down.
Different versions of CBT in the Hyper-V server and the proxy server.
Example: Consider you have two Arcserve UDP environments, one is Arcserve UDP Version 5 and another is Arcserve UDP Version 6.0. These two Arcserve UDP environments back up different VMs in the same Hyper-V server. The Arcserve UDP Version 6.0 environment automatically detects the older version of CBT in the Hyper-V server and upgrades it to the latest version. In such cases, the Arcserve UDP Version 5 environment converts the remaining scheduled incremental backup to a full backup.

If Arcserve UDP detects different CBT versions, the Activity Log displays a warning message.

The solution is to upgrade all the proxy servers that protects virtual machines from one Hyper-V host to the same version of Arcserve UDP.