RAID 1 error question - boot problem.
Bill Davidsen
davidsen at tmr.com
Fri Jul 24 22:03:36 UTC 2009
Robin Laing wrote:
> Hello,
>
> I am trying to help someone get a system to reboot after a system issue.
> He is not the builder of the system and the person that knows the
> system is away for a few weeks. Great timing. :)
>
> It is Fedora 10.
>
> Two drives, two partitions each drive which one is a mirror.
>
> /dev/sda is partitioned as /boot and / which is mirror 1.
> /dev/sdb is partitioned as swap and /
>
> The system wouldn't restart on the reboot and came up with an error
> after creating the raid arrays and then saying that it cannot find
> /dev/md0. I don't have the exact error message right now.
>
> Using an Ubuntu disk (persons personal preference) the system was booted
> into a live system and using gparted the partitions were shown to be as
> above with as I see it, one error.
>
> /dev/sda1 ext3 boot
> /dev/sda2 ext3 / raid
>
> /dev/sdb1 Swap
> /dev/sdb2 Unknown / raid
>
> Running mdadm /dev/sdb2 --examine shows that the partition superblock is
> showing RAID 1 and that it is clean.
>
> As this is a critical system, it is a priority and is being used as a
> virtual server.
>
> With only the second drive installed, we tried to run fsck.ext3 on the
> /dev/sda2 (normally b2) with no success. We also tried /dev/md0 as
> Ubuntu has created the /dev/md0 from the single drive.
>
> The user has not tried to boot with only the one drive in yet. He is
> making a copy of the drive on a different system.
>
> Now, the question. On booting from a mirror 1 array, if there is a
> problem with the raid system, how does the boot process read the
> mdadm.conf file when it is on the RAID array that needs to be created?
> Is there some data that is stored in the /boot or someplace else that
> has the necessary info to tell the system how to build the array?
>
> Is it part of the /boot/grub/device.map or /boot/System.map* ?
>
> Any suggestions to where to start?
>
The linux-raid group would have been a better choice, but this is a simple
question. The mdadm.conf file should get put in the initrd file, which is in the
/boot partition, which you didn't mirror for some reason. I'm guessing that sda2
is a better place to start, since that's recognizable as an ext3 partition.
Having a partition identify as "Unknown" is usually not a good thing. I would
mount that partition and copy the contents to a secure backup if this is critical.
"I don't have the exact error message right now" doesn't help, I suggest backing
up sda2, and sda1 if you can, noting the error message, and post back. Without
more information I am guessing that the sdb2 partition is in some way hosed, do
NOT run fsck on sda2 before backing up, and run with the "-n" option to see what
condition the f/s is in. I doubt you've lost your data yet, don't do anything
which would change that.
--
Bill Davidsen <davidsen at tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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