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Druva Documentation

VSS Basic Troubleshooting Guide

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This article applies to:

  • OS: All windows OS post  WS 2003
  • Product edition: inSync Cloud/On-Premise/Phoenix


This article provides the basic steps to resolve VSS issues before you address error messages or resort to advanced troubleshooting.

Troubleshooting steps

  1. Check Windows event logs:

    Check both the application and system event logs for detailed VSS errors. Subsequently, also check the Hyper-V VMMS events.
  2. Check third-party backup software:

    Check for any third-party backup software. If found, uninstall it and reboot the server.
  3. Check Shadow Storage Space:

       Check the storage on each server with the below command.
  vssadmin list shadowstorage {/for=<ForVolumeSpec> | /on=<onVolumeSpec>}

      Reference: vssadmin list shadowstorage

      Example: vssadmin list ShadowStorage /for=E:\ 


  1. If there is less shadow storage space allocated, increase the storage in accordance with the requirement or set it to unlimited.

    vssadmin resize shadowstorage /for=<ForVolumeSpec> /on=<OnVolumeSpec> /maxsize=<MaxSizeSpec>

    Example: vssadmin resize shadowstorage /For=E: /On=E: /MaxSize=UNBOUNDED
  2. Delete any stale and old shadow copies using the following command:

    Vssadmin delete shadows /all
  1. Check Writers StatusVSS backups fail if application-specific writer, such as hyper-v writer or SQL, fails.
    Check the writer status with the following command:

    Vssadmin list writers
    The output must include all the writers listed and must be in a stable state.
  2. Troubleshoot unstable/failed writers using the common steps:
    • Check the service account of the corresponding writer. Ensure it is a system account.
    • Check the event log.
    • Check the service of the corresponding writer. List of some corresponding services mentioned below:
      • Hyper-V Virtual Machine Management
      • SQL Server VSS Writer
      • Oracle VSS writer
      • System Writer
    • Restart the concerned service and run the above command again.
  3. Advanced troubleshooting steps for unstable/failed writers.
    • Restart COM+ System Application Service
    • Restart Distributed Transaction Coordinator Service
    • Restart Volume Shadow Copy Service
    • Restart the corresponding VSS writer service. For example, Hyper-V VSS writer or SQL VSS writer
  4. Re-register all VSS & COM+ components.

    Run the following command using elevated command prompt.

    cd /d %windir%\system32
    Net stop vss
    Net stop swprv  
    regsvr32 ole32.dll
    regsvr32 vss_ps.dll
    Vssvc /Register
    regsvr32 /i swprv.dll
    regsvr32 /i eventcls.dll
    regsvr32 es.dll
    regsvr32 stdprov.dll
    regsvr32 vssui.dll
    regsvr32 msxml.dll
    regsvr32 msxml3.dll
    regsvr32 msxml4.dll
    regsvr32 Vssapi.dll
    regsvr32 Vssui.dll  
    regsvr32.exe /i
    regsvr32.exe /i %windir%\system32\swprv.dll  
    regsvr32.exe %windir%\system32\vssui.dll  
    regsvr32.exe %windir%\SysWOW64\vss_ps.dll  
    regsvr32.exe %windir%\SysWOW64\msxml.dll  
    regsvr32.exe %windir%\SysWOW64\msxml2.dll
    regsvr32.exe %windir%\SysWOW64\msxml3.dll
    regsvr32.exe %windir%\SysWOW64\msxml4.dll
    regsvr32.exe %windir%\SysWOW64\ole32.dll  
    regsvr32.exe %windir%\SysWOW64\oleaut32.dll
    regsvr32.exe %windir%\SysWOW64\es.dll
    regsvr32.exe %windir%\SysWOW64\comsvcs.dll
    vssvc /register
    net start swprv
    net start vss
    net stop winmgmt  
    regsvr32 wmiutils.dll  
    net start winmgmt

  5. Multiple Providers
    • At the elevated command prompt, run the following command

      vssadmin list providers

    • The output must list one or maximum two providers as follows:

      • 'Microsoft Software Shadow Copy provider 1.0

      • Microsoft File Share Shadow Copy Provider

    • If there is any provider other than the above two, disable and stop the services corresponding to these providers. For example, the following providers.
      • Acronis VSS HW Provider
      • StorageCraft Volume Snapshot Software Provider
  6. To resolve any VSS-specific errors, use the solutions provided in the Troubleshooting VSS errors section.
  7. For advanced troubleshooting such as VSS trace, refer the Microsoft blogs: How VSS Tracing Works and Using Tracing Tools with VSS.