[CentOS] mdadm problem.

David Mackintosh David.Mackintosh at xdroop.com
Tue Sep 25 16:44:41 UTC 2007


So I'm trying to RAID-1 this system which has two identical disks
installed in it, and it isn't working for some reason.

I started by doing a CentOS-4 install on /dev/sda1 as root, and with
/dev/sda2 as my swap.

I finish the install, yum update, and then I want to make the mirrors.

I copy the partition table from one disk to the other:

# sfdisk -d /dev/sda | sfdisk /dev/sdb

I create my metadevices:

# mdadm -Cv -l1 -n2 /dev/md1 /dev/sdb1 missing
# mdadm -Cv -l1 -n2 /dev/md2 /dev/sdb2 missing

I create my filesystems:

# mkfs.ext3 /dev/md1
# mkswap /dev/md2

I change the /etc/fstab to use /dev/md1 for / and /dev/md2 for swap.

I change the /etc/grub.conf to use /dev/md1 for the root= parameter on my kernel.

I build myself a new initrd for the kernel I want to boot.

I copy the contents of / over to the one-armed mirror:

# cd /
# mnt /dev/md1 /mnt/md1
# tar cfpl - . | ( cd /mnt/md1 ; tar xfp -)
# umount /mnt/md1
# sync

I run grub just in case:

# grub
> device (hd0) /dev/sda
> root (hd0,0)
> setup (hd0)

I reboot, expecting that the system will find /dev/md1 and use it as
its root... but it doesn't.  Digging around in hobbled mode (changing
the root= parameter in grub to /dev/sda1 instead of /dev/md1) shows
that /dev/md1 doesn't get assembled, therefore it doesn't get mounted.

Can anyone tell me what I've done wrong?

-- 
 /\oo/\
/ /()\ \ David Mackintosh | 
         dave at xdroop.com  | http://www.xdroop.com
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