Re: Linux mdadm superblock question.

[Giovanni Tessore <giotex@texsoft.it>]

>>>> 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