what is running VSS on my server Client's SQL Server farm DBs are backed up by third-party tool that does not use VSS. About half of the instances show backups being made by some tool that is using VSS. I can disable SQL Server VSS Writer to stop these errant backups, but how do I track down what is running the VSS backups?

keywords: Volume Shadow Copy Service, volume-shadow-service [I don't have rep to create tags]
I believe that if you run native SQL Server backups (using T-SQL BACKUP) instead of DPM protection agent-based SQL backups, the SQL Server VSS Writer service must not be used on your SQL Server database folders.  (The same problem is true for other third-party backup tools.)

This DPM/VSS service is not used by native SQL backups. If you prevent the DPM protection agent backups from triggering SQL Server VSS snapshots, this will protect your chain of log backups.

If DPM/VSS does continue to backup the SQL Server files, then the log chain is broken, because there are two tools (T-SQL BACKUP and DPM/VSS) backing up the log files.