Occurs when an Acronis Backup task is started on the Hyper-V host, no matter which VSS provider is selected (or none). Manual VM snapshots are working. The error might be also appear in combination with CAPI2 errors. Operating systems seems not to matter: 2008 R2 / 2012 R2 / 2016.
Event ID 8229, VSS, 0x800423f4 prepareforsnapshot
First read the official Acronis VSS troubleshooting guide, but in fact, this is not Acronis‘ fault.
If you use AD GPO, make sure your Acronis user (and also user NT Network Service) is allowed to logon as a service. Starting with Windows 8 / 2012 R2, hidden group „NT Virtual Machines“ needs this permission.
Check if you can make manual disk shadow copies. If you have connected any external USB HDD drive, also make sure it works for them, or disconnect them.
For the CAPI2 error, look here. You can paste the quite complex permission command from there, afterwards this error should be gone.
sc sdset MSLLDP D:(D;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;BG)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;SY)(A;;CCDCLCSWRPDTLOCRSDRCWDWO;;;BA)(A;;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;SO)(A;;LCRPWP;;;S-1-5-80-3141615172-2057878085-1754447212-2405740020-3916490453)(A;;CCLCSWLOCRRC;;;SU)S:(AU;FA;CCDCLCSWRPWPDTLOCRSDRCWDWO;;;WD)
For me, running chkdsk finally solved the issue:
chkdsk /f /r c:
Choose to run it on next system boot, and run it for every partition you have.
This solved the issue in my case. A few weeks ago, I resized the hidden OS and system partition by a 3rd party partitioning tool, which might have caused the error (some missing file or wrong link in the hidden shadow copy store etc.).
This SU thread led me to the solution.
If chkdsk does not help and the error appears only for single VMs, try to uncheck the „Backup (volume checkpoint)“ integration feature within the VM’s properties. Reference