@torontob:
1- I want to know how the backup can be triggered? Would OS boot automatically fall to the second partition if the first fails?
2- Would it be by simply choosing option 2 at boot time?
3- What is the way to set the mirror as the default at start-up?
4- Are the configurations copied between the two mirrors as a system is built? If not, really this other partition is useless and waste of space isn't it? Since, it's probably much more cleaner and might take the same time to re-image the whole thing anyhow.
you have to choose it at boot time.
yes
Diag>Nanobsd
there is one shared config partition.
It's primarily if you want to upgrade one and have the option to revert back to the previous version. (with caveats for drastically different versions, like 1.2.3 vs. 2.0, where the configs aren't compatible)