If you see error messages like the following in the Message Logs of the backup:

VSS Snapshot Creation failed. Check Log file for more details.
Warning: Plugin VssPlugin do_VSS failed.
Warning: Plugin VssPlugin Post VSS failed.
Running as 'SYSTEM'. Privmask=00000206
VSS PLUGIN start backup job
Warning: Plugin VssPlugin finish_VSS failed.


The VSS failure you are seeing on the backup is due to insufficient storage space available to create the VSS snapshot.

The actual error text in the trace files is: "Error text: VSS_E_INSUFFICIENT_STORAGE"


Run systeminfo from Diagnostics and you can see the available resources for the server.

If this is a Virtual Machine (VM), you may be able to devote more system resources to that server and get away from the error.

See [Microsoft Docs]({:target=\_blank} for further details.

-it suggests looking for and if possible, deleting old shadow copies.