On 10/03/2014 01:04 AM, Chris Murphy wrote:

On Oct 1, 2014, at 12:33 PM, "Wilson, Jonathan"
[off-list ref] wrote:

quoted

From what I can tell with UEFI I need to set up a UEFI partition
with a FAT format.

It's a particular kind of FAT, that's defined as EFI FAT, the idea
being that if the originating FAT ever changes, EFI FAT won't.

quoted

On my current BIOS system I have a Biosboot 1M, /boot Raid1 200M
and / Raid 1 40G.

Obviously Grub installs to the mbr, and then installs a bit into 
Biosboot which can read raids, hence it can read and boot from
/boot.

BIOSboot applies to GPT disks on BIOS computers, not MBR. On MBR
disks, the GRUB stage1 code jumps to stage2 code in the MBR gap which
is the region between the MBR and the first partition's starting
LBA.

quoted

Further, from what I can tell, into the UEFI partition can go
either a kernel & initramfs with UEFI support, or a "loader" that
then loads the kernel.

No. An OSLoader is required, it's an EFI application. Its job is to
load a kernel and initramfs. The kernel and initramfs could be on the
ESP (EFI System partition) but this is fraught with limitations. The
expectation is that the kernel and initramfs are on some other
partition of the same disk. Of course if you're using GRUB it doesn't
care and will find a kernel/initramfs off another disk also, or even
off md raid.

An option to consider is to compile a kernel using the EFI stub option,
a pre-set command line, and an embedded initramfs.  Then the kernel can
boot directly from the EFI FAT partition with *no bootloader*.  The
embedded initramfs can support any raid/lvm/partitioning scheme
what-so-ever.

http://kroah.com/log/blog/2013/09/02/booting-a-self-signed-linux-kernel/

The cryptography is optional if you just want to boot really fast.

If your BIOS can be configured to try multiple boot images, it should be
possible to have true raid fallback without using motherboard or
hardware raid.  (Set up md raid1 with metadata v1.0 of multiple copies
of the EFI FAT partition.)  I've been meaning to try this....

Phil