On 01/10/2014 17:33, Wilson, Jonathan wrote:
I've just been struggling with exactly this trying to move my gentoo
system on to raid ...
From what I can tell with UEFI I need to set up a UEFI partition with a
FAT format.
I believe so, yes.
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.
Is this grub1, or grub2? I gather grub1 actually CAN'T read raid, which
is why you need to use raid version 0.9. Grub then thinks the disk is
plain ext4 or whatever, and reads it fine. grub2 actually handles raid,
and therefore is happy with newer raids like 1.2
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.
What I am unsure about are...
1) Can the loader/kernel understand md raid? so the / can be in a bog
standard raid1 v1.2?
Don't think so. Apparently the kernel can NOT put a raid array together
so you have a catch-22 - the kernel needs the raid in order to start
user-space, but it needs user-space in order to find the raid ... :-(
So you need an initramfs to solve the conundrum. And of course, grub1
doesn't work with uefi :-(
2) I'm guessing I would no longer need the /boot as that would be
replaced by what ever was in the UEFI partition?
You do need /boot - not least so grub2 can find its config file (that's
not quite true, but close enough...)
3) as my "/boot" is currently in a raid 1 my life is simple, should any
changes occur they are replicated to the drives I have set up as /boot
raid 1, and I installed the mbr portion of boot loader manually on each
disk and tested pulling one, and then booting from another.. it
worked :-)
In the world of grub2/raid1.2 I wish things looked that simple. From my
"badly burned novice" viewpoint, I don't think it is.
So I would like to keep things, if not simple, at least less likely to
have problems because I forgot to install duplicates of the UEFI on all
the disks... so can I use a .90v raid1 on the UEFI partition, then
format it as fat... so that all copies of what ever is in the UEFI
partition are replicated across the multiple raid1 disks, instead of
having to remember to copy what ever is in there manually to ach disk?
Interesting idea ... but I get the impression that once you've set up
the uefi partition and got it working, you shouldn't normally ever need
to go back to it. This is, I think, one of those cases you need to set
up a crib sheet and not do anything without it, as you'll forget from
one time to the next (which is why, I think, you want to use raid :-)
Personally, I *wouldn't* want to use raid, on the assumption that I'm
going to screw it up and don't want a mirror trashing disk2 as I trash
disk1.
Cheers,
Wol
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