VSS Writer Failed / How to Restart and Re-Register VSS Writers

ISSUE

VSS writers can fail for various reasons, such as two or more resources trying to use the writer at the same time.  When you run vssadmin list writers in a command prompt with admin rights, you might see one of the writers in a failed state, as shown below:

vssadmin list writers

Writer name: 'Microsoft Hyper-V VSS Writer'
   Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
   Writer Instance Id: {c35d6ab0-9588-412f-ae7b-cdc37534501f}
   State: [8] Failed
   Last error: Retryable error

RESOLUTION

It is important to identify if the issue is transient or if the issue is persistent and requires further diagnosis.  The process below will temporarily resolve most VSS errors, however the cause of that failure may repeat unless independently addressed.  

VSS is a native windows component and it if is failing changes usually are required to windows or other environment behaviors in order to permanently resolve.  Understanding which VSS component is impacted is a key step and whether the issue can be simply reset temporarily or remains in a failed state.  

That said, restarting a windows service may resolve the issue temporarily and allow a manual backup to succeed.  The steps below will temporarily reset many VSS issues: 

1. On the Windows server in question, open a command prompt with administrative rights and run the command

   vssadmin info
   
   vssadmin list writers

2. Check the writers that have failed.  
3. You can use the list below to find the service that corresponds to the VSS Writer in question.  Restarting the corresponding windows services in many cases will resolve the VSS issues.  
4. Use the vssadmin list writers command again to show if the vss writer is now in a stable state.  Re-attempt your operation and determine if the writer fails again.  
5. If the vss writer remains in a failed state after restarting the related service, or immediatly fails again when attempting a backup, you should identify the specifics of the VSS error with further troubleshooting by identifying the specific VSS HREF code in windows.  Additional detailed information is contained in the linked articles below the chart.  

NOTES

This KB covers common VSS error codes and details on potential cause and resolution steps. 

Again VSS is a native windows service.  Backups do not cause these services to fail.  They fail because VSS is not in a healthy state or runs into software conflicts when a backup requests a snapshot from Windows.  Other underlying conditions in windows, software corruption, antivirus software interference, improperly completed OS updates, software installations done without required reboots, multiple backup products installed in the same machine, under-configured windows resources or storage performance bottlenecks, and more can cause this issue.  Identifying the cause of your VSS issue may not be trivial and in some cases requires expert support from Microsoft itself to resolve.  Rarely can a change from a backup vendor alone resolve or work around VSS issues.  The above information however may be useful in troubleshooting which service is impacting the operation.