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Old 06-21-2012, 04:39 AM
Rob Kampen
 
Default CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

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

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

On Wed, Jun 20, 2012 at 1:00 AM,<m.roth@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
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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CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos


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Old 06-21-2012, 06:34 AM
Arun Khan
 
Default CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

On Thu, Jun 21, 2012 at 10:09 AM, Rob Kampen
<rkampen@reaching-clients.com> wrote:
.... snip ....

> sounds like the mirror is not in synch - when it is running with both
> drives, what does
>>cat /proc/mdstat

System boots up fully functional with both disks
<copy-paste>

root@centos62-raid1 ~ >
# cat /proc/mdstat
Personalities : [raid1]
md_d0 : active raid1 sda[0] sdb[1]
10485696 blocks [2/2] [UU]

unused devices: <none>

</copy-paste>

Both disks are in sync.

Anyways, even if they were out of sync the system should boot with the
"disk" that is in "U" state but it does not.

System boots up in rdshell (failed mode) with one of the disks disconnected.

<cat /proc/mdstat>

# cat /proc/mdstat

Personalities:
md_d0: inactive sda[0] (S)
10485696 blocks

</cat /proc/mdstat>

I do not know the internal workings of "dracut" but the problem seems
to be within it (gut feeling).

-- Arun Khan
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Old 06-21-2012, 06:10 PM
Scott Silva
 
Default CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

on 6/20/2012 11:34 PM Arun Khan spake the following:
> On Thu, Jun 21, 2012 at 10:09 AM, Rob Kampen
> <rkampen@reaching-clients.com> wrote:
> .... snip ....
>
>> sounds like the mirror is not in synch - when it is running with both
>> drives, what does
>>> cat /proc/mdstat
>
> System boots up fully functional with both disks
> <copy-paste>
>
> root@centos62-raid1 ~ >
> # cat /proc/mdstat
> Personalities : [raid1]
> md_d0 : active raid1 sda[0] sdb[1]
> 10485696 blocks [2/2] [UU]
>
> unused devices: <none>
>
> </copy-paste>
>
> Both disks are in sync.
>
> Anyways, even if they were out of sync the system should boot with the
> "disk" that is in "U" state but it does not.
>
> System boots up in rdshell (failed mode) with one of the disks disconnected.
>
> <cat /proc/mdstat>
>
> # cat /proc/mdstat
>
> Personalities:
> md_d0: inactive sda[0] (S)
> 10485696 blocks
>
> </cat /proc/mdstat>
>
> I do not know the internal workings of "dracut" but the problem seems
> to be within it (gut feeling).
>
> -- Arun Khan
>
Just a shot in the dark... DO all the fstab entries call out md devices?



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Old 06-23-2012, 04:44 AM
Arun Khan
 
Default CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

On Thu, Jun 21, 2012 at 11:40 PM, Scott Silva <ssilva@sgvwater.com> wrote:
> on 6/20/2012 11:34 PM Arun Khan spake the following:
>> On Thu, Jun 21, 2012 at 10:09 AM, Rob Kampen
>>
> Just a shot in the dark... DO all the fstab entries call out md devices?
>

Yes, /etc/fstab contains /dev/md_d0p1 for / partition.

I have been doing some digging in the initramfs and the dracut script.

The initramfs does contain all the md related stuff like drivers, the
devices for md_d0 and the /etc/mdamd.conf. To the best of my
knowledge these should be sufficient to load /dev/md_d0p1 (/).

I have not had a thorough look at the dracut script though.

I will post whatever relevant information if I find something that I
don't quite understand.

-- Arun Khan
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http://lists.centos.org/mailman/listinfo/centos
 
Old 10-15-2012, 10:32 AM
Arun Khan
 
Default CentOS 6.2 on partitionable mdadm RAID1 (md_d0) - kernel panic with either disk not present

__ SOLVED __

On Sat, Jun 23, 2012 at 10:14 AM, Arun Khan <knura9@gmail.com> wrote:
>
> I have not had a thorough look at the dracut script though.
>

I also posted this problem on the mdadm mailing list but could not get
the problem resolved.

So did some searching on the suspect candidate 'dracut'

After some more searching I found these two bugs reports:
CentOS 6.2 <http://bugs.centos.org/view.php?id=5400>
CentOS 6.3 <http://bugs.centos.org/view.php?id=5970>

Using "System Rescue CD" and mounting the disk image files, I appended
'rdshell' to the kernel line in grub.conf.

With 'rdshell' one can at least do the following to get the system operational.

Booted the system with a disk failure

At the rdshell prompt:

# mdadm --run /dev/md_d0
(replace device name with your device name)

# cat /proc/mdstat
(make sure your raid device is active with one member failure)

# CTRL-D
(exit the rdshell)

The system will boot with md_d0 in degraded mode.

Login in to the system.

# yum update dracut
(dependency dracut-kernel is pulled in)

As of this writing it is dracut-004-284.el6_3.1.noarch

# cd /boot
# dracut <initramfs file name> <kernel version>

Update grub and reboot.

System boots with when either disk has failed.

-- Arun Khan
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