Bug#534274: [mdadm] mdadm fails to assemble raid array on boot with kernel > 2.6.26

[Lior Chen]

Hi,

On Tuesday 23 June 2009 09:33:45 you wrote:
> also sprach Lior Chen <liorc at lirtex.com> [2009.06.23.0810 +0200]:
> > With kernels newer than 2.6.26-2 (I have tried both 2.6.29-2 and
> > 2.6.30-1) mdadm fails to assemble raid array on boot:
> >
> > Assembling all MD arrays... md: md0 stopped
> > mdadm: no devices found for /dev/md0
> > Failure: failed to assemble all arrays.
>
> Please look at
> http://wiki.debian.org/InitramfsDebug#Savingdebuginformation and try
> to provide as much information as you can about what happens between
> the boot loader and the initramfs prompt.
>
> > mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sda2 /dev/sdb2
> > or
> > mdadm -A /dev/md0 /dev/sda2 /dev/sdb2
> >
> > it fails saying that /dev/sda2 and /dev/sdb2 are busy (mdadm: Cannot open
> > /dev/sda2: Device or resource busy).
>
> It seems like som device mapper thing is getting in the way:
> > in the initramfs shell:
> > ls -l /dev/mapper :
> > control
> > isw_cjhfigcfig_LCRAID
> > isw_cjhfigcfig_LCRAID1
> > isw_cjhfigcfig_LCRAID2
>
> I have no idea what that is, but a sneaking suspicion that
> isw_cjhfigcfig_LCRAID2 is /dev/sd[ab]2.
>
> Try to disable that.

I have managed to fully reproduce this. This situation arose from mistakenly 
installing the dmraid package along with the mdadm package (or maybe it was 
installed because of some package-dependency, I can't really tell). 

Removing the dmraid package is not enough, and removing the mdadm package and 
reinstalling it again is required in order to update the initramfs. You were 
right about suspecting the  isw_* devices, they were generated by dmraid, and 
that was the problem.

The stranger thing is that this situation happens only with new dmraid 
versions (1.0.0.rc15*). Maybe the dmraid package should check for this conflict 
and warn the admin, because the result is an unbootable system.

Martin and Giuseppe -  Thanks again for helping me solve this.
Lior