Avamar: Hyper‑V Backups fail with Error 43426 during checkpoint creation

Avamar Hyper‑V backups fail or complete with exceptions.

All virtual machines hosted on a specific Hyper‑V node are excluded from the backup.
 

• The following error appears in the Avamar backup logs:

avhypervvss Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME_1><VM_GUID_1>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
avhypervvss Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME_2><VM_GUID_2>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
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avhypervvss Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME_X><VM_GUID_X>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
avhypervvss Info <0000>: --------------------Start [EMC Avamar Plug-in Service for Windows] log ----------

• Multiple VMs from the same Hyper‑V node show similar messages within the same backup job.

Additional log details are available in the winclustersvc.log file located at:

C:\Program Files\avs\var\

• This log is collected from the node that owns the Avamar backup cluster client, as identified in Failover Cluster Manager.

Example log entries:

winclustersvc WARN<0000>:  WMI API returned error: 'Failed to create checkpoint on collection 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>).
The operation failed.
Guest cluster validation on VM group 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>) failed for checkpoint creation.
Size of the VM group 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>) is not same with the size of the guest cluster.'  
winclustersvc DEBUG<0000>: <=== ValidateOutput  
winclustersvc DEBUG<0000>: Retry '1', WMI API 'CreateSnapshot' for VMGroup 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' 
winclustersvc DEBUG<0000>: ===> ValidateOutput  
winclustersvc DEBUG<0000>: WMI API return value is: '4096' 
winclustersvc DEBUG<0000>: Waiting for Job to complete... 
winclustersvc DEBUG<0000>: WMI job completed with status '10'  
winclustersvc WARN<0000>:  WMI API returned error: 'Failed to create checkpoint on collection 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>).
The operation failed.
Guest cluster validation on VM group 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>) failed for checkpoint creation.

• For these messages to appear, debug logging must be enabled for the winclustersvc service. Instructions are provided in the Additional Information section.

The Microsoft Windows Management Instrumentation (WMI) Application Programming Interface (API) generates checkpoint creation errors when several VMs from the same Hyper‑V node are selected in a single backup dataset. This limitation results in failed checkpoint creation and skipped VMs during the Avamar Hyper‑V image-level backup process.

Ensure Correct Hyper‑V Configuration:

• Install all recent Microsoft updates on the affected Hyper‑V node.
• Verify that none of the VMs use:
  • Disk sets
  • Shared disks
  • In‑guest Cluster Shared Volumes (CSV)

These configurations are not supported with Hyper‑V image-level backups.

Workaround
To reduce the likelihood of checkpoint failures:

• Use smaller VM groups in the backup dataset.
• Select fewer VMs from the same Hyper‑V node per backup job.
• Open a support case with Microsoft to investigate and address WMI API issues on the Hyper‑V node.

Enable Debug Logging for winclustersvc:

1. Using Notepad, create a file named winclustersvc.cmd in the following directory on the Hyper‑V node that owns the Avamar clustered client:

   C:\Program Files\avs\var\

2. Add the following entry:

   --debug

3. Restart the EMC Avamar Plug‑in Service for Windows.
4. Rerun the backup to reproduce the issue and collect detailed logs.