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Asked: 2015-07-24 00:04:21 +0800 CST

Veeam Hyper-V backup error: Microsoft Hyper-V VSS Writer VSS_WS_FAILED_AT_POST_SNAPSHOT

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I have an error from a Veeam Hyper-V backup of a Virtual Machine in a Hyper-V host:

Unable to create snapshot (Microsoft CSV Shadow Copy Provider) (mode: Veeam application-aware processing). Details: Writer 'Microsoft Hyper-V VSS Writer' is failed at 'VSS_WS_FAILED_AT_POST_SNAPSHOT'. The writer experienced a transient error. If the backup process is retried, the error may not reoccur. --tr:Failed to verify writers state. --tr:Failed to create VSS snapshot. --tr:Failed to perform pre-backup tasks.

I cannot understand if this is a host error, a guest error or Veeam error. I tried to reboot the VM but I got the same error. I did not try to reboot the host, but I tried to change the host (this VM is inside a failover cluster of two hosts) and with this change the backup works again.

During the backup failure I ran this command in the host:

 vssadmin list writers

The output was:

>    Writer name: 'Microsoft Hyper-V VSS Writer'
>        Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
>        Writer Instance Id: {f50fe40b-27d6-4a98-8713-e5a1dce54c97}
>        State: [1] Frozen

After the VM migrates to another host, the writer state changes back to "Stable".

What can freeze the VSS writers?

There is a 10103 event in the Host:

Failed to revert to VSS snapshot on the virtual hard disk '\\?\Volume{29e16157-002f-4cb4-af58-c95acbd54be9}\' of the virtual machine 'srvshare1'.
backup

1 Answers

  1. Is the virtual machine a domain controller?

    Have you tried below from http://www.veeam.com/kb1697

    vssadmin list writers

    The results will appear as:

    Writer name: 'NTDS' Writer Id: {b2014c9e-8711-4c5c-a5a9-3cf384484757} Writer Instance Id: {ee24b741-eaf7-4663-8f95-b92ae8c5e164} State: [1] Stable Last error: No error

    If not listed as stable reboot the DC.

    ────────────────────────────────────────────────────────── Verify that Automatic mounting of new volumes enabled. ────────────────────────────────────────────────────────── From a Run command (Win+R) execute the command diskpart.

    From within Diskpart run the following command.

    automount

    If the results do not show “Automatic mounting of new volumes enabled.” Run the following command:

    automount enable

    ────────────────────────────────────────────────────────── Verify that there are no .bak keys in the ProfileList within the Registry. ────────────────────────────────────────────────────────── From a Run command (Win+R) execute the command regedit.

    Within the registry navigate to:

    HKLM\Software\Microsoft\Windows NT\CurrentVersion\ProfileList

    There will be a list of Keys, you must remove any ending in .bak

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