Lost boot, two drives.

[rychok]

I'm writing this from pure curiosity, if someone knows how this works?
I have MGA 7 on Samsung 850EVO 120GB, with HDD RAID writing performance problem (I have posted about this and at this point it looks fine), so one of the solution was to install MGA 8. I used Samsung 840EVO 250GB. Before fully switching to MGA8 I was replacing drives to boot one of the system at the time. Everything was working till yesterday.
After shutting down MGA8 I have put MGA7 drive , and system did not boot, black screen with cursor going down like after pressing Enter key(no messages), I have switch back to MGA8 - same black screen. BIOS was not showing any EFI boot entry, after selecting boot drive in BIOS I got GRUB2 rescue console (both drives).
In the end I used MGA 8 installation USB drive to rescue the system (MGA8 drive), rebooted and system booted just fine. Next I wanted to do same for second drive but it also booted fine without any rescue procedure.
For me the explanation would be that somehow BIOS lost a way of detecting EFI partition, and pointing do drive started legacy booting where GRUB was not able to boot that way.
But if this was a BIOS so how rescuing system on one drive fixed it, so both drives were bootable again.

[sturmvogel]

https://unix.stackexchange.com/questions/484501/swapping-hard-drives-results-in-being-unable-to-boot

https://wiki.archlinux.org/title/GRUB#Default/fallback_boot_path

[filip]

It seems to me that rEFInd is more robust and is also officially packaged.