Windows server 2016 Hyperv-V Backup error "0x8078004F"

nraev 21 Reputation points

My windows backup backing up to NAS folder and worked fine, but now windows backup is failing with error code "0x8078004F"

The backup operation that started at '‎2021‎-‎06‎-‎19T18:00:07.880845800Z' has failed with following error code '0x8078004F' (The mounted backup volume is inaccessible. Please retry the operation.). Please review the event details for a solution, and then rerun the backup operation once the issue is resolved.

Event viewer says:
Application backup
Writer Id: {66841CD4-6DED-4F4B-8F17-FD23F8DDC3DE}
Component: 15ACC6A2-F544-4B2E-A3D7-55639A815409
Caption : Online\Server
Logical Path:

Backup works only for local hard drives (bare metal, c, d) and fails when backup start to copy Hyper-V. Only option to backup hyper-v is on externel USB HDD. Backup do not works on network folder. I tried to change location to another NAS, but i still have same error.

A Windows technology providing a hypervisor-based virtualization solution enabling customers to consolidate workloads onto a single server.
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Accepted answer
  1. Eleven Yu (Shanghai Wicresoft Co,.Ltd.) 10,686 Reputation points Microsoft Vendor


    After researching, I found your issue seems to be similar with the experiences mentioned in below thread.

    KB5001347 (April 2021 Update): Issue with Server Backup on Hyper-V Server 2016

    The issue occurs when attempting the backups to a synology NAS device. At the moment, the workarounds can be summarized as below:

    1. Backup to a windows-based network share.
    2. Uninstalling KB5001347 if installed
    3. Seek for assistance from support engineers of Synology



    If the Answer is helpful, please click "Accept Answer" and upvote it. Thanks.

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