[plug] Software raid issue - moving a raid set to a new system

Matt Kemner zombie at penguincare.com.au
Thu Nov 29 12:59:50 WST 2007

Hi Carl

> I've got a mirrored device md0 which on system A is sda1 + sdb1, and
> the OS disk is hda1,2,5
> When I move that mirror set to system B (with a SCSI OS disk) I was
> hoping that placing the drives as sdb and sdc would be autodetected.
> The result was the detection of sdb1(system A's sda1) as half the
> mirror, and not detecting the other half in sdc1.

Are the partitions set to type fd (raid auto detect) and is the RAID
support built into your kernel? (as opposed to a module)

If you do, the kernel should automatically scan all partitions, and
auto-build the raid arrays from any partitions flagged with fd.

If the kernel gets it wrong, try stopping the array and then reassembling
it manually with mdadm

mdadm -S /dev/md0

mdadm -A /dev/md0 -a /dev/sdb1 -a /dev/sdc1

Once assembled, the superblock on the drives will be updated, so it should
auto-mount correctly in future.

Kind Regards,

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