VSS_E_UNEXPECTED_PROVIDER_ERROR

Error

You might see one or more of these:

• VSS_E_UNEXPECTED_PROVIDER_ERROR
• [Shadow Copy] (4/4) Will retry in 60 seconds. The software retries the shadow copy, and the numbers show which attempt it’s on. If every attempt fails, it backs up without using VSS.
• The backup software stops unexpectedly.

Cause

This is a general Microsoft error. It means the Volume Shadow Copy Service (VSS) failed, but Windows doesn’t say why, so you need to work through the checks below to find the cause.

The causes we see most often are:

• A VSS writer has failed, or the VSS components need re-registering.
• Low disk space.
• Missing Windows updates.
• File paths longer than the Windows limit of 260 characters.

Fix

1. Install all Windows updates, and restart the device if asked.
2. Run a full antivirus scan.
3. Check there is plenty of free space on the drives being backed up.
4. In Event Viewer, check the Application and System logs for VSS errors around the time of the backup.
5. Open an elevated Command Prompt (right-click Command Prompt and click Run as administrator) and run:

   vssadmin list writers

   A writer has failed if its State isn’t Stable or its Last error isn’t No error. Restarting the device usually clears a failed writer.
6. If none of these finds the cause, run the backup software in debug mode and attach the log to a support ticket. The log shows exactly where the backup fails.

We don’t recommend the registry changes suggested on other websites. They rarely fix VSS problems and can stop VSS working altogether.