A Windows server's backup jobs keep failing with an error message stating that the source drive is not available. After reviewing the logs, which of the following should a technician do FIRST to…

Verifying the backup media has enough storage space is crucial for backup completion, but the error 'source drive is not available' points to an issue with reading the data from the source, not writing to the destination.

The Volume Shadow Copy Service (VSS) is essential for creating consistent backups of files and applications while they are in use by taking 'snapshots' of volumes. If VSS is not running or malfunctioning, backup applications will fail to access and copy open files, leading to 'source drive not available' errors because a stable point-in-time image of the data cannot be created.

Closing terminal services sessions is generally unrelated to a source drive availability issue for backup purposes, as backup software typically runs as a system service with elevated privileges, independent of user sessions.

While rebooting can sometimes resolve transient issues, it is a general troubleshooting step. Given the specific error about the 'source drive not available,' verifying the VSS service, which directly impacts data accessibility for backups, is a more targeted and efficient first step than a blind reboot.