Shadow Copy Component backup of Windows 2008 Cluster Node fails with Status Code: 156 - Snapshot Error Encountered

Problem

 Shadow Copy Component backup of Windows 2008 Cluster Node fails with Status Code: 156 - Snapshot Error Encountered

Error Message

In the Event Viewer, Application log the following event is logged:

Cause

The backup operation fails because Automated System Recovery (ASR) unnecessarily returns an error for noncritical disks. The expected behavior is that ASR returns an error when critical disks are not available. ASR then logs a Warning event for noncritical disks. However, ASR returns errors when both critical disks and noncritical disks are not available. 

Solution

Apply the Microsoft HotFix mentioned in KB967560   (https://support.microsoft.com/kb/967560)

OR

As a workaround step, run the following command:

w2koption -backup -ignore_unresolved_paths drive_letter

Use the actual drive letter for the unavailable disk, example:

w2koption -backup -ignore_unresolved_volumes X:

To confirm the command took, execute the following command:

w2koption -backup -display

The resulting output would be similar to this:

C:\Program Files\Veritas\NetBackup\bin\w2koption -backup -display

NetBackup Backup Options
-----------------------------------------
System State Backup: Disallow legacy backup
KMS Activated Server Backup: Disabled
EFI Boot Enabled Backup: Disabled
Ignore Unresolved Volumes: X: <------- see here that the X: drive is excluded.
Snapshot Provider Type: VSS Selects Provider 

It is recommended that determining why the network path is broken be investigated. 
If there are more than one unresolved volume, you have to ignore all volumes with one command.  For example:

w2koption -backup -ignore_unresolved_volumes X:Y:Z:

To remove the setting, run the same command without drive letter(s):

w2koption  -backup -ignore_unresolved_volumes

Applies To

NetBackup 7.x
Windows 2008 Cluster node