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Hyper-V Backup fails with Disk Merge error HYPERV23
Updated over a week ago

Title: Hyper-V Backup fails with Disk Merge error HYPERV23


  • HyperV virtual machine backup would fail with error HYPERV23.

  • The backup log would have below information on it

[2021-11-20 00:09:45,256] [ERROR] <_MainThread(MainThread)> Error <class 'inSyncLib.inSyncError.SyncError'>:Disk Merge of <Virtual machine Name> Failed: (#100090017) (Error Code : HYPERV23). Traceback -Traceback (most recent call last):
File "agentPartnerProcess.pyc", line 157, in _process_request
File "agentPartnerProcess.pyc", line 85, in _process_request_start
File "agents\hyperv\hypervAgent.pyc", line 70, in process_backup_start
File "agents\hyperv\hypervBackup.pyc", line 810, in backup
File "agents\hyperv\rctHelper.pyc", line 97, in post_data_upload
File "agents\hyperv\hypervapi\hypervMachine.pyc", line 522, inwait_for_pending_disk_merge_job
File "inSyncLib\inSyncError.pyc", line 30, in raise_error
SyncError: Disk Merge of VM <Virtual Machine Name> Failed: (#100090017) (Error Code : HYPERV23)


If there is a checkpoint existing which has not been merged and the backup job is unable to merge it.


Step 1:

  • Check if you can delete the checkpoint from the Hyper-V manager.

  • Power off the Virtual machine and then try to run a full/differential backup.

  • Then Power on the Virtual machine and test the subsequent backup.

Step 2:

  • Power off the virtual machine.

  • Then try to merge the snapshot from the Hyper-V manager by either deleting the existing checkpoint or merging the disk by following below Microsoft article.

See also

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