Source:Troubleshooting Hyper-V

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Hyper-V backup fails with error [ [NInternal::CVssAsyncDecorator::Wait] - VSS_S_ASYNC_PENDING]


  • The Hyper-V backup fails with the following error:
Error: DB Module: [ [NInternal::CVssAsyncDecorator::Wait] - VSS_S_ASYNC_PENDING]


  • You have to increase the VSS value in the configuration file <SESAM_VAR>/var/ini/sm.ini from 200

to 600


Hyper-V backup fails with time-out error


  • The backup task fails with a time-out error in Windows:
Error:   DB Module: [ [Failed at thaw] - VSS_E_WRITERERROR_TIMEOUT.
[Microsoft Hyper-V VSS Writer] - VSS_E_WRITERERROR_TIMEOUT]


Hyper-V backup fails with error VSS_E_SNAPSHOT_SET_IN_PROGRESS


  • When backing up a Hyper-V VM in Windows Server 2012, the following error appears:
Error: VSS_E_SNAPSHOT_SET_IN_PROGRESS error and in the Windows Event logs VDS basic provider error


Backup of a Linux VM fails


  • When backing up a Linux VM without Guest Services support, backup job fails with error:

Backups of Linux systems with Guest Services support work normally.


  • If backing up Linux VM fails with VSS_E_WRITERERROR_NONRETRYABLE error, open the VM Settings -> Integration Services and disable the option Backup (volume shadow copy).

Hyper-V restore fails


When attempting to restore a Hyper-V VM into a different Hyper-V environment, the restore might fail with one of the following errors:

Unable to import virtual machine due to configuration errors

or something like

The virtual machine <VM_name> is currently using an AMD processor, but physical computer 
<host_name> has an Intel processor. A running or saved virtual machine cannot be migrated to a physical computer that has a processor from a different vendor. 
However, you can move the virtual machine to this node if you shut down the virtual machine.

A configuration error may occur if a VM you want to restore is not compatible with the destination Hyper-V host. Restoring can fail for the following reasons:

  • Hyper-V VMs are using advanced CPU features and fail if the CPUs are too different (different generation, type ...), when restoring VMs between servers with different processor types, e.g., Intel VT or AMD-V, or when the destination server is lacking virtualization extensions or they are disabled.
  • Restoring a VM that is fully configured with virtual switches and network definitions into a different Hyper-V environment may result in the original switch definitions not being found.

Possible solutions

Check VM and Hyper-V host compatibility
Before restoring a VM to a different Hyper-V host, check whether the host can support the VM type you want to restore. Use the Compare-VM cmdlet to check a VM and a Hyper-V host compatibility. Run the following commands to first record the compatibility report in a PowerShell variable $Report and then display the compatibility report:
$report = Compare-VM -Path $Source
$report.Incompatibilities | FT -AutoSize

Use the report to fix any compatibility or configuration issues. For details, see MS article Compare-VM.

Enable processor compatibility mode for a virtual machine
According to Microsoft: "Hyper-V performs pre-flight checks whenever a virtual machine live migration or save/restore operation is initiated. These checks compare the set of processor features that are available to the virtual machine on the source host against the set of features that are available on the target host. If these feature sets don’t match, the migration or restore operation is cancelled." For more information, see the whole MS article Processor Compatibility Mode in Hyper-V. To enable processor compatibility mode for a virtual machine, proceed as follows:
The Processor Compatibility Mode is only applicable to processor types within the same vendor processor family. It does not enable migrations between AMD- and Intel-based hosts. For more information, check TechNet Magazine Tip: When to Use Processor Compatibility Mode to Migrate Virtual Machines.
  1. Open Hyper-V Manager and shut down the VM which you want to configure for CPU compatibility mode.
  2. Right-click the powered off VM. In the Action pane, click Settings, and then click Processor.
  3. Expand Processor, and click Compatibility.
  4. Click Migrate to a physical computer with a different processor, and then click OK.
Shut down VM, back up, and restore
If you are restoring a VM from a Hyper-V host with one processor type (e.g., AMD) to a host with a different (e.g., Intel), you might try to move a Hyper-V VM by shutting it down, backing it up, and then restoring on the new host.

Hyper-V Manager 2016 VM fails to boot after restore


After successfully restoring a Hyper-V virtual machine (VM), the restored VM may be unable to boot. This issue specifically affects Hyper-V Manager 2016 or older versions. The cause of the boot failure is the Secure Boot option, which can create a mismatch between the VM's boot configuration and the restored environment.


Disabling the Secure Boot option allows the VM to bypass the security checks that may be causing the boot problem. To disable the Secure Boot option:

  1. Shut down the restored VM in Hyper-V Manager 2016.
  2. Disable the Secure Boot option:
    • In the Hyper-V Manager select the VM and go to Settings of the VM.
    • Navigate to Hardware -> Security, and uncheck the option Enable Secure Boot.
    • Click Apply and then OK to save the changes.
  3. Start the VM in the Hyper-V Manager.

During mount of a Hyper-V RCT backup, a Windows Explorer window is opened for every mounted VHDX


During mounting of a Hyper-V backup, Windows Explorer window opens for every mounted vhd(x). This problem occurs on Microsoft Windows workstation OS if Autoplay is enabled for removable drives and option Open folder to view files (File Explorer) is selected.

Possible solutions

For removable drives set the option Take no action as default, or disable Autoplay completely.

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