[CentOS] CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

Tue Jun 19 19:30:28 UTC 2012
m.roth at 5-cent.us <m.roth at 5-cent.us>

Arun Khan wrote:
> On Wed, Jun 20, 2012 at 12:11 AM,  <m.roth at 5-cent.us> wrote:
>> Arun Khan wrote:
>>>    Device Boot      Start         End      Blocks   Id  System
>>> /dev/sda1   *           1         523     4194304   83  Linux
>>> Partition 1 does not end on cylinder boundary.
>>> /dev/sda2             523        1045     4194304   83  Linux
>>> /dev/sda3            1045        1176     1048576   82  Linux swap /
>>> Solaris
>> <snip>
>> Ok, I see that it's hardware 512b blocks, so you're not running into
>> issues with 4k hardware blocks. I trust you installed grub on /dev/md0,
>> which I assume is /dev/sda1 and /dev/sdb1?
>>From the wiki instructions, there is no re-installation of GRUB, only
> a couple of changes in /boot/grub/grub.conf file installed by the
> regular installation on /dev/sda.   During the RAID1 creation process
> the  grub from /dev/sda would mirrored into the RAID1 device and
> appear on the MBR of both the disks.
> As I said in the OP, I do see the grub menu with either of the disks
> "unplugged"  i.e. missing.   The kernel does boot and the white
> progress bar goes upto about 50% when the kernel panic occurs.  I will
> turn off the splash and see what comes up on the console.   Gut
> feeling --  I suspect the problem is with the initrd image created
> with the "dracut"

For one thing, edit grub.conf and get *rid* of that idiot rhgb and quiet,
so you can actually see what's happening. Sounds to me as though it's
trying to switch root to a real drive from the virtual drive of the ramfs,
and it's not working. One thing you *might* also try is before you boot,
edit the kernel line in grub, and add rdshell at the end, so you boot into
grub's rudimentary shell if/when it fails, and you can look around and
find what it's seeing.