OMV Gpart safe minimum size

Poor title sorry.

Understanding that any OMV install will likely have growth etc., I'm trying to harmonize my OS image backups for a variety of SD cards and also reduce the time for backups. Let's say my minimum card size is 16GB (I know that actual size varies from card manufacturer to card manufacturer) and I've offloaded my storage/media and Docker installs to another drive(s).

I have a clean clone of the current install but as we know Armbian will extend itself out over any available space so I want to gpart things down to a minimal size with sufficient headroom.

I was just use 8GB as my standard but even that seems high. I get there's a lot of factors at play here but anyone who's been at this for a while have a reliable partition size for their clones images? Perhaps my logic is entirely flawed here to begin with...apologies in advance.

Thanks for the solid info here.

One other question: are/have you enforced any partition shrink (via something like gparted) or are you just always cloning from 16gb card to 16gb cards?

Excellent, thanks very much. This is very clear.

Sorry for all my rookie questions lately but you all have really helped me totally transition my home (off-grid/solar powered) environment.

With that method can you simply burn those files to new card? Seems too good to be true!

Very interesting, thanks! The 2 partitions on the SD card is a good idea.

Seems like there's 2 general schools of thought around here about disaster recovery:

1. Just keep Cloning SDs, when one dies pop in a new one.
2. Backup OS files (to safe location) for later recovery.

or something like that....