[iam-TJ]

It is NOT possible to have the UEFI access the RAID device so that if one of the mirrors is broken it can continue to boot in degraded mode.

It requires manual intervention of a knowledgable person to boot a UEFI system into the default OS if the ESP is broken or missing.

[effie]

OK now I get what you mean. In that case, one can reboot and select the other non-broken disk and the system will boot, with some hiccups due to degraded array, but it will boot.