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Linux Software RAID 10 seems pretty good. Not sure what magic makes it work but I can even remove /dev/sda and it boots fine. Perhaps grub installed on every drive? Hmmm.
@adamd
did you find any "official" or at least concise documentation of RAID?
I'm afraid of it to be honest. Badly configured raid means you lose everything on a single drive failure.
@_vasilis_ Hmm. I found some documentation but mostly a lot of experimenting. Pulling drives, recovery, reboot, adding drives, hot spare, etc. It seems pretty good. Lots of reading.
@adamd my understanding is that you can configure it such that GRUB is installed on every drive, yeah.