Many times we have backups, of Windows servers and VMs, fail because one or more VSS writers fail. The backup logs and event viewer would indicate that a VSS shadow copy operation failed for various reasons and this may leave the VSS writer in a Failed state as seen below
Many times a reboot may resolve the issue but obviously it is not always possible to restart the server, especially if there are a number of applications running on it or multiple virtual machines. Instead you may want to find the relevant service and restart it to try and refresh the state of the VSS writer.
To find the VSS writer that failed, you will need to open an elevated command prompt and execute the command:
vssadmin list writers |
The console will list all the VSS writers installed/available in windows and among them you may find some with a failed state.
Writer name: 'Microsoft Hyper-V VSS Writer'
Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
Writer Instance Id: {b063f91d-4768-471e-9687-5b56f9c8bb30}
State: [7] Failed
Last error: No error |
The above shows the ‘Microsoft Hyper-V VSS Writer” is in a failed state. To reset the VSS writer and you will need to restart the Hyper-V Virtual Machine Management service. Run the command again to ensure that the VSS writer is in a Stable state
Writer name: 'Microsoft Hyper-V VSS Writer'
Writer Id: {66841cd4-6ded-4f4b-8f17-fd23f8ddc3de}
Writer Instance Id: {b063f91d-4768-471e-9687-5b56f9c8bb30}
State: [1] Stable
Last error: No error |
Note: This has fixed the issue for me on many occasions but sometimes you may need to re-register the VSS writers or you may be running out of disk space. It is important to check the Event log to understand better what is causing the VSS writer to fail. Sometimes there is no other way around it and you would need to restart the server or vm.
As you may know, there are more VSS writers that could fail. When this happens I end up Googleing to find the associated service to restart. To have them handy for myself and hopefully for anyone else that comes across this, below is a list of the VSS writers name and associated Service to restart.
I go the list from the Dell AppAsure KB129774 and willtry to update it if I find new ones.
| VSS Writer | Service Name | Service Display Name |
|---|---|---|
| ASR Writer | VSS | Volume Shadow Copy |
| BITS Writer | BITS | Background Intelligent Transfer Service |
| COM+ REGDB Writer | VSS | Volume Shadow Copy |
| DFS Replication service writer | DFSR | DFS Replication |
| DHCP Jet Writer | DHCPServer | DHCP Server |
| FRS Writer | NtFrs | File Replication |
| FSRM writer | srmsvc | File Server Resource Manager |
| IIS Config Writer | AppHostSvc | Application Host Helper Service |
| IIS Metabase Writer | IISADMIN | IIS Admin Service |
| Microsoft Exchange Writer | MSExchangeIS | Microsoft Exchange Information Store |
| Microsoft Hyper-V VSS Writer | vmms | Hyper-V Virtual Machine Management |
| NTDS | NTDS | Active Directory Domain Services |
| OSearch VSS Writer | OSearch | Office SharePoint Server Search |
| OSearch14 VSS Writer | OSearch14 | SharePoint Server Search 14 |
| Registry Writer | VSS | Volume Shadow Copy |
| Shadow Copy Optimization Writer | VSS | Volume Shadow Copy |
| SPSearch VSS Writer | SPSearch | Windows SharePoint Services Search |
| SPSearch4 VSS Writer | SPSearch4 | SharePoint Foundation Search V4 |
| SqlServerWriter | SQLWriter | SQL Server VSS Writer |
| System Writer | CryptSvc | Cryptographic Services |
| TermServLicensing | TermServLicensing | Remote Desktop Licensing |
| WINS Jet Writer | WINS | Windows Internet Name Service (WINS) |
| WMI Writer | Winmgmt | Windows Management Instrumentation |
Hope you found this useful. Let me know in the comments section!