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Backups fail with one of the following errors:



If this error appears during Differential or Incremental backups of databases, please review the following article instead:

Info: How do databases handle backups from multiple different backup applications?

This behavior accounts for an overwhelming majority of VSS Writer issues related to Microsoft SQL Server, Microsoft Exchange, and Microsoft SharePoint.

What's going on?

Zmanda Cloud Backup utilizes set of built-in Windows functions known as Volume Shadowcopy Services, or VSS, to create snapshots of data for backup.


It is possible to check the state of all writers on the system using the vssadmin list writers command.

vssadmin list writers

The vssadmin list writers command will list all of the writers currently available on the machine as well as their current state. Run vssadmin list writers from an elevated (Run As Administrator) command prompt.


  • A writer in the Stable state is ready and waiting to take a backup.
  • Writers in the Failed or Unstable states have encountered a problem, and may need to be reset by restarting the controlling service.
  • Writers that are currently Waiting for Completion or In-Progress are in use by some process. Cancel any backup that is running, or wait for it to complete, before running a new backup.
    • If no backups are running, the writer should be reset like Failed or Unstable writers by restarting the controlling service.


There are many possible reasons that a VSS Writer can fail. The writer must be brought back to the Stable state before backups can function.


Verify that all requirements are met before moving on to the solutions below.

Solution #1: Restart the controlling service

Most failed VSS Writer issues can be fixed with a simple restart of the service that controls the writer. This usually brings the writer back to its stable, working state.


Should the backup still fail, or if the writer is still not Stable, please check our Knowledgebase for related articles and known VSS issues.

Solution #2: Check for known VSS issues

Certain specific VSS Writer failures are well understood. These failures are discussed in our Knowledgebase.

Solution #3: Verify that Windows and the application to be backed up are both fully up to date

Microsoft has released many updates, patches, and hotfixes for VSS-related issues. Although this applies to all versions of Windows, the updates are relevant to Windows Server 2003 most of all.


Please ensure that the system is fully up to date.

Solution #4: Verify system health

VSS functionality can be compromised by failing hardware on the system. Problems with disk storage (such as full disks, failing disks, damaged RAID arrays, and the use of 4k drives on older systems) are particularly likely to cause VSS failures. However, hardware issues of any type can potentially impact the ability of the system to take snapshots using the VSS Writers.

If any problems are discovered, resolve them before attempting backups again.

Further troubleshooting

If none of the above information applies, the system and the VSS failures should be thoroughly investigated by the System Administrator for the system in question. The Windows Application Events and Windows System Events usually contain information about writer failures.