• Tom's Help Desk
    I have been recently seeing this error on one of our server's backup reports:

    'Microsoft Hyper-V VSS Writer' writer status is invalid. Try again later or see Event Log for more information. State: FailedAtPrepareSnapshot, Failure: WriterErrorRetryable

    The backup will complete manually without any issue, but when the job is run on schedule this error happens every time. The backup is running a single Hyper-V VM backup to B2 and had been working without issue for months until a week ago.

    If anyone could point me in the right direction to get this resolved I would really appreciate it.
    Thanks in advance,
  • Matt
    Updating integration Hyper-V integration services is the first thing that comes to my mind. Then, of course, re-registering VSS on both the host and guest VM. You might also want to try schedule the backup to the time of manual start and see if the issue persists. Maybe the service is preoccupied with something else at the time of the backup.

    Checking VSS event logs might also be a good idea.
  • Stratos Misinezis
    Hello. In most of the machines I do backups more than 20 I got this error everytime backup is executed. Backup is executed normally though but I am wondering what is the cause of this error.

    Volume Shadow Copy Service error: Unexpected error querying for the IVssWriterCallback interface. hr = 0x80070005. This is often caused by incorrect security settings in either the writer or requestor process.

    Gathering Writer Data

    Writer Class Id: {e8132975-6f93-4464-a53e-1050253ae220}
    Writer Name: System Writer
    Writer Instance ID: {cb38584d-ccb2-4d77-b005-d31134683e25}
  • Matt
    To solve your issue just do the following:
    - Start Menu > Run > dcomcnfg
    - Expand Component Services, Computers, and My Computer.
    - Right-click My Computer and click Properties on the pop-up menu > COM Security tab.
    - Under Access Permission click Edit Default.
    - From the Access Permissions dialog, add the "Network Service" account with Local Access allowed.
    - Close all open dialogs.
    - Start Backup Service under administrator account: go to Tools > Change Service Account, enter local -- administrator account name and password, click OK. The service will be restarted automatically.
    - Restart the computer.
  • Stratos Misinezis
    Hello Matt. From the time I followed your guide I have now this error in Application Log

    Cryptographic Services failed while processing the OnIdentity() call in the System Writer Object.

    AddCoreCsiFiles : BeginFileEnumeration() failed.

    System Error:
    Access is denied.
  • Matt
    You might want to follow the instructions here or re-register VSS components

    First of all, make sure VSS works outside of our software.
  • Carlos
    Thanks again for the answer, seems that still works.
  • lburr
    Last month we upgraded from Server 2012 to Server 2019 with one VM (domain controller). The Hyper-V scheduled backup ran fine on Server 2012, but on Server 2019 it always fails with the following error:

    'Microsoft Hyper-V VSS Writer' writer status is invalid. Try again later or see Event Log for more information. State: FailedAtPrepareSnapshot, Failure: WriterErrorRetryable

    When I check the VSS writers (command prompt, VSSadmin list writers), Hyper-V VSS Writer has State: [1] Stable and Last Error: No Error.

    I found a note in https://www.msp360.com/resources/blog/troubleshooting-vss-volume-shadow-copy-issues/ regarding domain controllers:

    MSP360 Backup uses VSS Microsoft Service. During a backup of a Domain Controller issues might occur with VSS. If it happens, disable VSS in MSP360 Backup on the Backup Wizard step and retry the backup. If that doesn't help, please contact our support team.

    I've gone through the Hyper-V Backup Wizard but I'm not seeing an option to disable VSS.

    Any ideas? Scheduled file backups run fine, but I'm having to run Hyper-V backups manually.
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