I have an Intel box with two m.2 slots and have purchased 2 identical SSD’s to have one as a backup in case of failure. Initially I looked at Debian and RAID 1, however, I’d lose HA OS benefits and there still wouldn’t be an easy way to recover the OS in case one drive fails.
So I’ve tried installing HA OS on both drives whilst one being disconnected, which has worked however I’m unable to select which one to boot from in the BIOS. I’m also getting this issue in HA:
At
/dev/nvme1n1p8, we detected another active data disk (containing a file systemhassos-datafrom another Home Assistant installation).You need to decide what to do with it. Otherwise Home Assistant might choose the wrong data disk at system reboot.
If you don’t want to use this data disk, unplug it from your system. If you leave it plugged in, choose one of the following options:
Select submit to make
/dev/nvme1n1p8the active data disk. The one and only.You won’t have access anymore to the current Home Assistant data (will be marked as inactive data disk). After reboot, your system will be in the state of the Home Assistant data on
/dev/nvme1n1p8.
Mark as inactive Data Disk
Clicking the second option has resulted in it being repaired, not showing any more info, like the first option 
How do I mark this as active again??
Maybe this should be a feature request but I think this is the easiest way to recover a failed/failing SSD, by having a backup HA OS ready to be restored without having to pull the thing apart?