Please consider: https://community.openhab.org/t/openhabian-problem-after-upgrade/23446/8
Shouldn’t it be the other way around? The system can be lost and reinstalled. What you want to store in a safe place (e.g. a RAID inside a NAS) is your configuration. I’d suggest to either boot from network completely or have a complete SD card setup with a decoupled backup running against your NAS. @sihui mentioned RaspiBackup endless times and it’s exactly what you should be looking in in the second scenario.