Re: GPT on RAID

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Wed, 28 Sep 2022 13:53:42 +0300
    From:        Dima Veselov <kab00m%lich.phys.spbu.ru@localhost>
    Message-ID:  <4fd66e90-86f4-9fc3-aaf8-27ce417b1b74%lich.phys.spbu.ru@localhost>

  | I put GPT on RAID device (because disk is large) and it seems no good 
  | way to root autoconfig.

That's probably true, with the emphasis on "good" - but there is a way.

  | If there any way to autoconfig or tell kernel via bootloader that
  | my root reside on certain GPT partition which is on RAID device which
  | is on GPT of two disks?

I've had a setup essentially like that for years - you need to configure
the raid with "-A root" to tell raidframe to claim the root partition
(and autoconfigure itself), and the tricky (not good) part, the GPT
partition that is to be the root must have a wedge name of raidNa (where
raidN is the raid set).

So,
	gpt label -i M -l raidNa raidN

(M is the relevant partition index).   Don't forget to change any
relevant NAME= entries (in fstab, or elsewhere)
 to match.

	raidctl -A root raidN

It is somewhat bizarre, but works.

My system has:

NAME=raid7a             /               ffs     rw,log           1 1

in fstab, and raid7 includes...

raidctl -s raid7
Components:
            /dev/dk8: optimal
           /dev/dk18: optimal
No spares.
Component label for /dev/dk8:
   [...]
   RAID Level: 1
   Autoconfig: Yes
   Root partition: Yes
   Last configured as: raid7
[and the same for dk18]

and

gpt show -l raid7
       start        size  index  contents
           0           1         PMBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34         990         
        1024     1047552      1  GPT part - "raid7a"
(etc).

I don't think it is important (or even relevant) that the root partition
happens to be the first one in the gpt on the raidframe.


kre