[CentOS] Strange behavior from software RAID

[Gordon Messmer]

On 03/02/2013 06:35 PM, Harold Pritchett wrote:
> When I boot the system, I end up with two unexpected, unconfigured
> volume groups.

"RAID set" is a better term.  The term "volume group" describes 
components of the LVM system, which is not directly related to md raid.

>  Where the heck are /dev/md125 and /dev/md127 coming
> from?

Well, md125 is the other half of md1.  Check which of those two devices 
has the correct data.  Destroy the other, then add that partition to the 
remaining RAID device.

> They don't appear in /etc/mdadm.conf and if I re-boot they
> keep coming back.  It appears that somewhere mdadm is keeping
> information.  How can I get rid of it so the mdadm.conf file is
> used.

I think you'll need to do two things.  First, automatically-detected 
RAID sets get an automatic minor number assigned.  That number is stored 
in the RAID metadata, so if you want to change it, you'll need to 
manually update the metadata.  I think that's done by:
mdadm --stop /dev/md127
mdadm --assemble /dev/md2 --update=super-minor /dev/sdd3 /dev/sdb3

As Maxim suggested, you may also need to re-build your initrd.

As always, make sure you have backups first.