[CentOS] moving software RAIDed disks to other machine

Ross S. W. Walker RWalker at medallion.com
Sun Jul 20 19:14:25 UTC 2008

Kai Schaetzl wrote:

> I just replaced two md-raided (RAID1) disks with bigger ones and decided 
> to check out how far I get with them when I put them in another machine.
> The kernel boots and then panics when it wants to mount the root 
> filesystem on the disk.
> md: Autodetecting RAID arrays
> md: autorun
> md: autorun DONE
> < not sure if this means it was successful or failed, I 
> rather think it 
> failed because it doesn't list any md devices? >
> Creating root device
> Mounting root filesystem
> EXT3-fs: unable to read superblock
> I pxe-booted in rescue mode. Interestingly, the rescue mode detects and 
> mounts the RAID partitions just fine and mdadm sees them all as healthy. 
> It mounts them under /tmp/md0 and /tmp/md1. Shouldn't the installed system 
> be able to do the same, mount under /dev/md0 and /dev/md1 and then find 
> root on /dev/md1 as told by grub.conf? Or could it be that the installed 
> system also mounts them under /tmp?
> I'm not sure how I can troubleshoot this.

Most likely different controller, or controller order recorded in the
initrds of the drives. Rescue CD has it's own initrd, so it doesn't
have this problem.

Try to either, 1) rearrange the drive order in the bios to match the
old system, 2) find out what controller the new system is using and
stick in a modprobe line for it while the drives are back in the
old system and make an initrd, then move the drives over to the
new system.


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