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

Rob Kampen

rkampen at reaching-clients.com
Thu Jun 21 04:39:06 UTC 2012

On 06/21/2012 04:11 AM, Arun Khan wrote:
> On Wed, Jun 20, 2012 at 10:06 AM, Arun Khan<knura9 at gmail.com>  wrote:
>> On Wed, Jun 20, 2012 at 1:00 AM,<m.roth at 5-cent.us>  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
> 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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