I would like to join this conversation, because I have a similar question about backup and more importantly, RESTORE :).
As far as I understand, there are different backup ways and please correct me, if I'm wrong.
Option 1: Backup plugin
Backup: Archive running OMV installation disk with (preferably) fsarchiver onto same shared folder (locally, USB stick or remote mounted share)
Restore: Starting RescueCD from grub and point to archive file
Option 1: USBbackup plugin
Backup: Rsync running OMV installation disk onto attached USB device
Restore: ? not sure how to do it
Option 3: Clonezilla
Backup: Boot into Clonezilla from grub and clone disk to attached USB storage.
Restore: Starting Clonezilla from grub and restore the cloned disk
Clonezilla means downtime and manual work, correct?
Do all options protect against complete disk failure? OMV is installed on a SSD and it has to be replaced physically
Did I forget or misunderstand any option or procedure?