Symptoms
Hyper-V 2016 RCT backups may fail or complete with exception errors similar to the following:
avhypervvss Error <43426>: Checkpoint creation for Virtual machine 'DELLEMC1<VM GUID>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
avhypervvss Error <43426>: Checkpoint creation for Virtual machine 'DELLEMC2<VM GUID>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
...
avhypervvss Error <43408>: Failed to create RCT checkpoint for the targets.
avhypervvss Error <41674>: Failed to backup targets. Unable to snapshot targets.
avhypervvss Error <41659>: Backup did not complete successfully
From the winclustersvc.log (in C:\Program Files\avs\var directory of the Hyper-V host cluster node):
winclustersvc ERROR<0000>: Failed to execute CreateSnapshot method: GetErrorEx() call on the job failed.
winclustersvc DEBUG<0000>: <===RctCreateCheckpointForVMCollection.
winclustersvc INFO<0000>: Exception in Checkpoint creation on vmgroup 'AvamarBackup_CLUSTERNODE002-app-20181106042xxxx-0' : Failed to create checkpoint for groupname AvamarBackup_CLUSTERNODE002-app-2018110604xxxx-0.
winclustersvc DEBUG<0000>: Getting recalculated vhd info for the targets
winclustersvc DEBUG<0000>: Connect with namespace '\\CLUSTERNODE002\root\virtualization\v2'
winclustersvc DEBUG<0000>: ===> RecalculateVhdInfoAndRctId
winclustersvc INFO<0000>: RCT Checkpoint failed for VM 'DELLEMC1'. Skipping disk info recalculation
Cause
The skipped VMs are unable to create an "application-consistent" snapshot. Application-consistent snapshot consistency level is the default option in the Avamar Hyper-V VSS dataset configuration. Other causes include outdated Integration Services, failed VSS writers on the VM, etc.
Resolution
Merge orphaned snapshots and created separate datasets for application-consistent and crash-consistent snapshots.
Additional Information
Application-Consistent Backups are the default Hyper-V VSS setting within Avamar.
- All activity of the guest OS is paused
- If the particular application is supported, its VSS Writer can be paused (SQL Server Writer, Microsoft Exchange Writer, etc)
- The snapshot is created
- The guest OS's activity is resumed
- The application's VSS Writer (SQL Server Writer, Microsoft Exchange Writer, etc) is resumed
Support for particular application's handling will depend on the particular VM environment design; Service Pack levels, Proxy configuration and version, Support Tools, etc. may also affect this.
Crash-Consistent Backups takes no consideration for applications within a VM.
- All activity of the guest OS is paused
- The snapshot is created
- The guest OS's activity is resumed.