Possible causes of and remedies for status code 156 failures in Hyper-V backups

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When Hyper-V snapshot jobs are unsuccessful, frequently it is status code 156 (snapshot error encountered) reported.  This error is very commonly reported when snapshots start for a specific volume when something is wrong in configuration.  To resolve this issue, the configuration needs to be corrected at the VMware/Hyper-V snapshot client level.

This document provides some common causes of Hyper-V VM snapshot failure with status code 156 reported and the remedies which may be used to resolve them.

Error Message

snapshot error encountered

Status Code: 156


Refer to the table below:

Causes of status code 156
Description and recommended action
The virtual machine name is incorrectly specified in the NetBackup policy.
Indicates a mismatch between the virtual machine names that are specified on the policy Clients tab and the actual names on the Hyper-V server. Check the actual names as listed in the Hyper-V Manager on the Hyper-V server.
The following are the recommended actions:
  • In the NetBackup policy, the virtual machines must be specified as fully qualified names.
  • In the NetBackup policy, the virtual machine name may have been entered incorrectly.
If you browsed for the virtual machines on the Clients tab and selected names from the list, the list may be out of date. (The list is derived from a cache file.) Refresh the list by clicking on the icon next to the Last Update field.
Volumes on the virtual machine are almost full.
Specifies that volumes on the virtual machine do not have enough free space for the snapshot. Microsoft recommends that at least 10% of the virtual machine volume is available for the snapshot.
Recommended action: create more space on the volume
The Hyper-V integration component is absent.
Specifies that the Hyper-V integration component is not properly installed in the virtual machine
Make sure the proper version of the Hyper-V virtual machine integration component is installed on the virtual machine.
The integration component should be at version 6.0.6001.18016 or later. It should also be the same version as
drive_letter \Windows\System32\vmms.exe on the Hyper-V server. Otherwise, the backup fails with status code 156.
To determine the integration component version, right-click on the following file on the virtual machine and click Properties > Details:
drive_letter \Windows\System32\vmicsvc.exe
Windows NTFS shadow storage is configured on a different volume.
Specifies that for a Windows NTFS file system, Windows shadow storage for a volume (such as C:) must be configured on the same volume.
For a Windows NTFS file system, Windows shadow storage for a volume must be on the same volume. For example: If the virtual machine has multiple volumes, and the shadow storage for the C: volume is on the D: volume, the backup fails with NetBackup status 156. An error message similar to the following appears in the Windows event logs for Hyper-V VMMS:
An unhandled exception was encountered while processing a VSS writer event callback. The VSS writer infrastructure is in an unstable state. The writer hosting process must be restarted in order to resume VSS functionality.
Windows event logs for VMMS can be located on the Server Manager console
under the following:
Diagnostics > Event Viewer > Applications and Services Logs > Microsoft >
Windows > Hyper-V-VMMS > Admin
Do the following and re-run the backup.
The VSS framework in the virtual machine is not working properly
Specifies that the following application error event may be written to the virtual machine during backup:
Event Type: Error
Event Source: VSS
Event Category: None
Event ID: 12302
Date: 1/8/2009
Time: 1:36:21 AM
User: N/A
Volume Shadow Copy Service error: An internal
inconsistency was detected in trying to contact
shadow copy service writers. Please check to see
that the Event Service and Volume Shadow Copy Service
are operating properly.
For more information, see Help and Support Center at
Recommended action:
Run the vssadmin list writer command. If no writer is listed in the output and a similar error is logged, refer to the following to resolve this issue:
A CSV timeout occurred
Specifies that the bpfis log contains the following:
VssNode::prepareCsvsForBackup: CSV TimeOut expired, Not all required CSV available in required state.
One or more or the required cluster shared volumes (CSV) cannot be prepared in the specified timeout period. A current backup that started from another node needs one or more of the same CSVs.
Increase the Clustersharedvolumestimeout period and rerun backup, or try the backup at another time.
Enable offline backup for non-VSSVMsoption
is disabled
Specifies that the bpfis log contains the following:
VssNode::prepare Backup type of VM [<VM GUID>] will be OFFLINE and configuration parameter allowOfflineBackup] is not set. To backup this VM, set [allowOfflineBackup] configuration parameter.
NetBackup is not allowed to perform an offline backup of the virtual machine, because the Enable offline backup for non-VSS VMs option is disabled.
Enable the Enable offline backup for non-VSS VMs option.

Related Articles

Status 156 on Hyper-V Backup - The Hyper-V integration component is missing.

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