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

Rob Kampen <rkampen@xxxxxxxxxxxxxxxxxxxx> · Thu, 21 Jun 2012 16:39:06 +1200

On 06/21/2012 04:11 AM, Arun Khan wrote:

On Wed, Jun 20, 2012 at 10:06 AM, Arun Khan<knura9@xxxxxxxxx>  wrote:

On Wed, Jun 20, 2012 at 1:00 AM,<m.roth@xxxxxxxxx>  wrote:

.... snip ....

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.

Will try your suggestion and report back.

As mentioned already there are no issues with both disks connected.
In this scenario, I have changed the "Partition ID" of the
partitionable RAID1 partitions  /dev/md_d0p1 and /dev/md_d0p2 to 'fd'
and then rebooted the system (recall earlier these partitions had
Id=83).

I also made the suggested changes to /boot/grub/grub.conf by Mark

Rebooted the system with both disks connected - system boots fine.
Messages are displayed including the md driver binding /dev/sda and
/dev/sdb.     The  "root" device /dev/md_d0p1 is detected and it is
mounted on / and life is hunky dory.

Reboot the system with disk1 removed, the kernel boots, the 'md'
driver  tries to bind sda.  At this point the systems seems to hang
for a few seconds and then 'dracut' reports that it cannot find
/dev/md_dop1 (the root partition)

          dracut Warning: No root device "block:/dev/md_d0p1" found

sounds like the mirror is not in synch - when it is running with both 

drives, what does

>cat /proc/mdstat
show??

Console image pasted here<http://imagebin.org/217229>

In the "rdshell" environment I can see that /etc/mdadm.conf is defined
but beyond this I don't know what to look for.

Changing the Partition Id for the RAID1 partitions to 'fd' does not help.

Any further suggestions and/or comments?

-- Arun Khan
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