VSS_E_UNEXPECTED_PROVIDER_ERROR

Errors

1. VSS_E_UNEXPECTED_PROVIDER_ERROR
2. [Shadow Copy] (4/4) Will retry in 60 seconds. If there is a standard VSS error, our software retries the shadow copy ten times before timing out and backing up without using VSS.
3. The backup software crashes out.

Cause

This is one of those Microsoft errors, which means I don’t know what happened, so have this error code!!

You should go into Doctor mode and look for the presence of the abnormal or the absence of the normal.

Our experience with this error:

The VSS writers have failed to load.
The VSS writers need re-registering.
Low disk space.
The server’s OS and patch level are out of date.
File names longer than the 256 char limits. This confuses VSS and often throws the error above.

Fix

These are the fixes we tried.
Many other sites recommend tweaking and deleting parts of the registry, but this doesn’t make sense if you know how the VSS architecture works.

1. Check that the server’s OS and patch level is current. Use Windows Update for this.
2. Check that the server is virus-free.
3. Check that there is plenty of free disk space.
4. Check the Windows event logs for any other suggestions. The application and system logs are the best ones to check.
5. Run this command in a new CMD window vssadmin list writers. Look for any failed writers.
6. If nothing is obvious, run our software in debug mode. This will show the exact place where the backup fails.