Resolving Veeam Agent Backup Errors: "Creating VSS Snapshot Error"

Issue Summary

When using Veeam Agent for Microsoft Windows to perform backups, you may encounter the following error: Creating VSS snapshot error....Cannot create shadow copy of the volumes containing the writers data.

This error indicates that Veeam was unable to create a Volume Shadow Copy (VSS) snapshot, preventing the backup job from completing successfully.

Cause

The error typically occurs due to one or more of the following reasons:

• Insufficient free space on the disk where the snapshot is being created.
• Conflicting VSS writers or services running on the system.
• VSS errors or corruption in the Windows event logs.
• Security or permission issues preventing VSS from running.
• Other backup software interfering with VSS operations.

Resolution Steps

1. Check Available Disk Space

Ensure that there is sufficient free space on the disk where the shadow copy is being created. Typically, at least 10% of the total disk size should be available.

1. Open File Explorer and check the available space on the affected volumes.
2. If the disk is full, free up space by deleting unnecessary files or expanding the volume.

2. Restart VSS Services

Restarting the VSS-related services may resolve the issue.

1. Open Command Prompt as Administrator.

2. Run the following commands:

   net stop vss
   net start vss
   

3. Restart the backup job in Veeam and check if the issue persists.

3. Verify VSS Writers Status

1. Open Command Prompt as Administrator.

2. Run the following command:

   vssadmin list writers
   

3. If any writers are in a "Failed" state, restart the affected service(s) or reboot the system.

4. Check Event Viewer for VSS Errors

1. Open Event Viewer (eventvwr.msc).
2. Navigate to Windows Logs > Application.
3. Look for any VSS-related errors and resolve them based on the error message provided.

5. Ensure No Conflicting Backup Software is Running

VSS can only be used by one backup application at a time. If another backup solution is running, it may conflict with Veeam.

1. Check if Windows Backup or any third-party backup software is installed and disable it.
2. Restart the backup job in Veeam.

6. Increase Shadow Storage Size

If shadow storage is insufficient, increase it manually:

1. Open Command Prompt as Administrator.

2. Run the following command to check the current shadow storage allocation:

   vssadmin list shadowstorage
   

3. Increase the size using:

   vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20%
   

   (Adjust C: to match the affected volume and modify the max size as needed.)

7. Reboot Your PC

Sometimes, a simple reboot can resolve VSS-related issues by clearing any stuck VSS instances.

1. Save all your work and close any open applications.
2. Restart your computer.
3. After rebooting, retry the backup job in Veeam.

8. Run Veeam Backup Job with Application-Aware Processing Disabled

If the issue persists, try disabling application-aware processing. Note that this is not an ideal solution, as it may lead to crash-consistent backups instead of application-consistent ones:

1. Open Veeam Agent.
2. Edit the backup job settings.
3. Locate Application-Aware Processing and disable it.
4. Save changes and retry the backup job.

Conclusion

If none of the above steps resolve the issue, consider updating Veeam Agent and checking for Windows updates.