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VSS V-79-40960-38521 error

Level 1

Hi everyone,

BE 20.1 is not able to backup a 2008R2 VM guest on a 2012R2 Hyper-V Host. I get the V-79-40960-38521 error:

V-79-40960-38521 - Snapshot Technology: Initialization failure on: "VRTSRV::\\host\Hyper-V?Virtual?Machine\guest". Snapshot technology used: Microsoft Volume Shadow Copy Service (VSS). A virtual machine snapshot could not be created. Use the Event Viewer on the Hyper-V host to identify the cause. If the virtual machine is not properly configured, it may be necessary to use the Event Viewer in the virtual machine to identify the cause.

In the event viewer of the host I see event ID 8229:

A VSS writer has rejected an event with error 0x800423f4, The writer experienced a non-transient error. If the backup process is retried, the error is likely to reoccur. Changes that the writer made to the writer components while handling the event will not be available to the requester. Check the event log for related events from the application hosting the VSS writer.

PrepareForSnapshot Event

Execution Context: Writer
Writer Class Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
Writer Name: Microsoft Hyper-V VSS Writer
Writer Instance ID: {a0558640-36ec-41c6-b921-0226b45ed8c1}
Command Line: C:\Windows\system32\vmms.exe
Process ID: 2276

I saw there is Microsoft KB patch available that is supposed to solve the problem but its already installed on the host and I couldn't find a patch for 2008R2 server (guest)