Glad to hear the upgrade went mostly well. Was that from 8 to 9? I see they have released 9.1.x so may give a go on one node to see how it goes.
On the backup question, I don’t know of a native way through GUI of accomplishing this. May I suggest you take a look at multi-Report from @joeschmuck as it can accomplish what you want to do.
https://github.com/JoeSchmuck/Multi-Report
Check the documentation specifically in the Advanced section pg 34 where you can enable a scheduler for backing up the configuration files. There is an email and a save to local disk presuming your USB is available you can do that. Scripts is run periodically or daily through crontask.
Other HDD functions could be disabled if you choose not to use them.
Config-Backup
Configuration Backup Enabled (true)
o Set to ‘true’ to enable backups.
Save a local copy of the config-backup file (false)
o Set to ‘true’ will create a copy of the TrueNAS configuration in the path identified
below.
Day of the week would you like the file attached? (Mon)
o The day of the week to attach the TrueNAS backup file. Options are: Mon, Tue,
Wed, Thu, Fri, Sat, Sun, All, or Month.