Creating Plans to Protect Data › How to Create a Host-Based Virtual Machine Backup Plan › Troubleshooting › Host-based Backup Fails for Hyper-V VM That Has a Special Differencing Disk Configuration

Host-based Backup Fails for Hyper-V VM That Has a Special Differencing Disk Configuration

Valid for Hyper-V VM

Symptom

If a differencing disk is configured in a Hyper-V virtual machine, the backup job for that virtual machine fails. It displays the following error message in the activity log:

Failed to prepare for backup of the virtual machine

The following error message is displayed in the backup job log file under C:\Program Files\Arcserve\Unified Data Protection\Engine\Logs,

The virtual disk file \\?\UNC\<IP_Address_VM>\HYPERV_HBBU_SNAPSHOT@<snapshot_name>\WIN12-SQL\VIRTUAL HARD DISKS\WIN12-SQL-1.VHDX was not exposed.

The problem occurs only when the virtual machine has the following differencing disk configurations. All the configurations must apply.

• The virtual machine has one regular virtual hard disk (Fixed size or Dynamically expanding) Disk1 that is attached to one IDE or SCSI controller of the virtual machine.
• The virtual machine has one differencing virtual hard disk (Disk2) that is also attached to one IDE or SCSI controller of the virtual machine.
• The parent disk of Disk2 is specified to Disk1.

Solution

This error occurs because of an abnormal or incorrect configuration. To resolve this error, detach either the differencing disk or its parent from the virtual machine. Arcserve UDP does not support such differencing disk configuration.