backupServer is a DisplayString reporting whether the gateway's scheduled backups to an external disk backup server are succeeding, including a specific "Can't backup to xxx yyy zzz" alert issued when none of the configured servers are reachable. An admin depending on automated configuration backups can use this alert to catch a broken backup job before a needed restore point turns out to be missing. For example, seeing "Alert: Auto Backup Servers: Can't backup to server1 server2 server3" tells the admin all three configured backup targets are currently unreachable and backups are failing entirely.