/boot on RAID1 with fedora21

[Gordon Messmer]

On 05/15/2015 04:29 PM, Alex Regan wrote:
>> However, on UEFI, /boot/efi on RAID is not supported.  I'm not sure I
>> understand all the reasons for that, but I'm actually going to be
>> experimenting this weekend to see whether that works for a partition
>> with 0.90 or 1.0 metadata, and a system that does not boot Windows.
>
> That would be great.

Sorry to say that the one system I have where I can test this has a 
Gigabyte motherboard with a buggy UEFI (Hybrid UEFI) implementation.  It 
resets the EFI boot order in between boots, so nothing that is set with 
"efibootmgr" persists.  Spent a while on that before giving up.

So, I still don't know whether an EFI System Partition can be RAID 1 
with metadata 0.90 or 1.0.  I can't find any documentation that gives a 
reason why it can't.

If anyone else wants to test that out, I think the following would be a 
good way to start. (but only do this on a test system, because you might 
destroy everything)

# Set an unused md device name
raid=/dev/md125
# Set your EFI boot partitions
efip1=/dev/sda1
efip2=/dev/sdb1

# Save /boot/efi
cd /boot
tar cf efi.tar efi

# Create the RAID device
umount /boot/efi
mdadm --create "$raid" --level=1 --raid-devices=2 \
	--metadata=0.90 "$efip1" "$efip2"

# Create the filesystem
mkfs -t vfat "$raid"

# Get the UUID of the new filesystem
blkid "$raid"
# Fix the entry for /boot/efi in /etc/fstab
vi /etc/fstab
# If you got the previous two steps right, the filesystem will mount
mount /boot/efi

# Restore /boot/efi
cd /boot
tar xf efi.tar

reboot