1280 - Error when backing up many SQL databases on a single machine

Symptom

If you have a very large number of SQL databases (50+) on a single machine, you may encounter a variety of VSS and system errors. Some of these include:

• "Cannot create worker thread."
• "AddLegacyDriverFiles: Unable to back up image of binary Microsoft Link-Layer Discovery Protocol."
• "BACKUP DATABASE is terminating abnormally."

Solution

If the machine is running a 64-bit Windows OS, you can resolve this by increasing the max worker threads to three per database, as explained on Microsoft's Tech Community here. For example, if you have 200 databases, set the max to 600 threads. 

To do this using SQL Server Management Studio:

1. In Object Explorer, right-click a server and select Properties.
2. Click the Processors node.
3. In the Max worker threads field, type or select the appropriate number.

Note: This may significantly increase CPU and RAM usage at the time of the snapshot.

Once this has been done, schedule a reboot of the server and try the backup again. 

For more information on max worker threads, see this article from Microsoft's knowledge base.