Nextcloud - Backup / Restore Questions

Hi all,
I recently purchased a Odroid HC2 soley for the purpose of local backup for my families personal files, pictures, etc. and determined that Nextcloud would be the ideal way to access in home and out of home. I currently have 1 2 TB hard drive hooked up to my OMV 4 install and Nextcloud installed with no issues and MariaDB. I want to add another 2nd 2TB drive in solely for backup. I have a few questions though so I can ensure that backups are going correctly and how I would swap drives in case of failure...
What is the best backup method to "clone" the Nextcloud 2 TB drive to the 2nd drive? Basically I'd just want to ideally swap drives if it ever failed and move on with no data loss or (hopefully) time loss.
And if any such failure happened, is there a specific process or steps to properly follow to switch to the other drive, and then add a replacement for backup?