PBX Platforms - How to Setup Software Raid after the fact

If you ever need to setup Software Raid on a box after you have already installed your Distro you can following the steps below.

mdadm will ask which MD arrays are needed for the root fs. Go with the default (all)

yum install mdadm initramfs-tools vim

Add raid1 to /etc/modules

echo "raid1" >> /etc/modules

Regenerate initrd.img file

mkinitramfs -o /boot/test -r /dev/mapper/pve-root

Rename old img file (replace .x for whatever kernel version you are using)

mv /boot/initrd.img-2.6.18-2-pve /boot/initrd.img-2.6.18-2-pve.original

Rename new img file

mv /boot/test /boot/initrd.img-2.6.18-2-pve

Make sure grub is setup on both hdds

grub-install --no-floppy /dev/sda
grub-install --no-floppy /dev/sdb

Change UUID for (hd0,0) on /boot/grub/menu.1st if your file has the UUID in it. This most likely involves replacing the root UUID=XXXXX line with root hd(0,0)

# nano /boot/grub/menu.1st

Change UUIDs for proper md0 devices on /etc/fstab if your file has the UUID in it.
Now do the same thing for the /etc/fstab file.
Replace the UUID=XXXXXXXXX /boot ext3 defaults 0 1 line with /dev/md0 /boot ext3 defaults 0

# nano /etc/fstab

Clone the partition table from 1st drive to 2nd

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

Create md devices with second drive only

mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-devices=2 missing /dev/sdb2

Save new mdconf file

mdadm --detail --scan >> /etc/mdadm/mdadm.conf

Get boot device setup

mkfs.ext3 /dev/md0
mkdir /mnt/md0
mount /dev/md0 /mnt/md0
cp -ax /boot/* /mnt/md0
umount /mnt/md0
umount /boot; mount /dev/md0 /boot
sfdisk --change-id /dev/sda 1 fd
mdadm --add /dev/md0 /dev/sda1

Setup data device

pvcreate /dev/md1
vgextend pve /dev/md1

This step takes a LOOOOONG time

pvmove /dev/sda2 /dev/md1
vgreduce pve /dev/sda2
sfdisk --change-id /dev/sda 2 fd
mdadm --add /dev/md1 /dev/sda2