I recently reinstalled my systems, and I had to use superblock 0.9 to be
able to boot ext4 from raid-1 (kernel 2.6.31 - grub2 1.97-beta4).
I didn't go deep with it as I was quite in hurry, so I'm not sure if it
depends by grub2 or by kernel's md autodetection at boot.
I used superblock 1.1 for the others md devices.
mdadm 1.0 block devices, since stored at the end, can still be used
/read only/ the same way that 0.90 devices were used before grub knew
how to talk to them. By looking at the underlying block devices and
ignoring their tails. This does however only hold for raid-1 layouts
with the 1.0 or 0.90 format labels.
I guessed so, infact I created superblock 1.0 for the raid-1 devices md0
(root) and md1 (swap), while 1.1 for the others .. but it didn't work and I
had to revert to 0.9 for root and swap ...
Just a guess, but did you tell grub root was /dev/md0 or did you say
root was /dev/sd(whatever backs md0) ?
Root was set to (md0), I followed the installer of the distro (ubuntu
9.10 srv) and also tried manually with update-grub and then grub-install
/dev/sda, grub-install /dev/sdb, grub-install /dev/sdc (3 disk raid-1)
Both failed with superblock 1.0, giving a message like 'missing mapping
of device /dev/md0', infact into /boot/grub/device.map it was missing
(even for 0.9), but also adding it ( (md0) /dev/md0 )didn't help, giving
other error messages.
Btw, even if I missed something, the point is:
- with 0.9 it worked painless
- with 1.0 it didn't work
donno if it dependes by distro, kernel of md, but some different
behaviour relative to superblock 0.9 and 1.0 existed.
I didn't investigate further as I was in extreme hurry to setup the system.
Regards
--
Cordiali saluti.
Yours faithfully.
Giovanni Tessore
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