A backup fails with the error "Timed out waiting for VSS operation to complete".
Backup failed: Timed out waiting for VSS operation to complete (20 minutes)
Cause and solution
The timeout may have different causes.
If the error "Could not start VSS snapshot preparation (0x80042316; snapshot set in progress)" appears in the logs, it is likely that an instance of VSS is already running elsewhere, making VSS unavailable to the Redstor backup agent. To resolve this, ensure that the schedules of tasks that require VSS do not overlap.