What is the superblock version of the mdadm?
Only version 0.9 can be auto-detected by the kernel, other, newer,
versions (1.0,1.1,1.2) cannot (grrr).

You need to change your initramfs / initrd to have a more flexible method 
of detecting the drives, like using the --super-minor option.

On Thu, 29 Apr 2010, [email protected] wrote:

> Date: Thu, 29 Apr 2010 20:18:30 -0400
> From: "[email protected]" <[email protected]>
> Reply-To: Montreal Linux Users Group <[email protected]>
> To: [email protected]
> Subject: [MLUG] LVM2 on raid 5 screw up ... my own fault
> 
> Good evening all,
> Long time list member, but quasi first-time poster.
>
> I believe I screwed up my file server, it's non-operational at the moment, 
> but 100% recoverable, I just don't know how.
>
> Here's my setup:
>
> * Debian 5 on amd64
> * 5x 1TB drives (mostly 7200.12's)
> ** all partitioned as
> *** 1GB (sd*1)
> *** 999GB (sd*2)
> ** sda1, sdb1 = software raid 1 for /boot (others sd*1 are free or swap) (md0)
> ** sd*2 = software raid 5 for LVM2 (md1)
>
> I recently grew the array from 4 to 5 disks, resized my volume group, resized 
> my logical volumes and accompanying FS's. Last time I had done it (3 to 4 
> disks), it went fine. It worked great post reboot. However, this time, I 
> can't get past an initramfs shell.
>
> This time, I forgot to edit /etc/mdadm/mdadm.conf and tell it md1 has 5 
> devices, and not 4. I believe I hadn't rebooted since (a while back), and got 
> caught last night when I finally did.
>
> So, when I boot, I get stuck in an initramfs shell. The previous console 
> messages are about software raid of course:
>
> mdadm: /dev/md0 was started with 2 drives
> mdadm: no devices found for /dev/md1
>
> Wait, what?
>
> Here's the thing, I can do this little mdadm/lvm dance leading to me being 
> able to mount all my logical volumes. If memory serves me right, it went 
> something like this:
>
> mdadm --assemble --scan /dev/md1 /dev/sda2 /dev/sdb2 /dev/sdc2 /dev/sdd2 
> /dev/sde2
> lvm vgchange FirstGroup -a y
>
> At this point, /proc/mdstat says /dev/md1 is fine with all its 5 disks, 
> lvscan will tell me my volumes are all active. I can mount in r/w. I took the 
> liberty of editing /etc/mdadm/mdadm.conf to reflect 5 instead of 4 drives, 
> but that doesn't make it boot any better. Nor should it, really. The system 
> can't even read mdadm.conf because it's not even mounted, so I don't see how 
> that file has any effect on the issue. But perhaps there's a side effect, 
> some background process that does I don't know what.
>
> I re-read the documentation I used to grow the array 
> (http://scotgate.org/2006/07/03/growing-a-raid5-array-mdadm/), and there are 
> no last critical steps that sort of commit the changes survive a reboot, my 
> process was the same as last time, except editing mdadm.conf.
>
> So, there's something wrong with initrd or something of the sort.
>
> I'm not pulling my hair out like I did last night, I know it's 100% 
> recoverable, but it's just kind of annoying to have a system sit there not 
> knowing what to do.
>
> Does anyone have a clue? Reinstalling *is* a possibility, given my partition 
> scheme, but would prefer not to at this point in time. I'll be googling in 
> the mean time.
>
> Thanks,
> Lawrence
>
> Sorry if this post is a little verbose, figured i'd be as clear as possible.
> _______________________________________________
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>
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