this is basically how I setup the raids. It is following  the software raid howto.


modprobe raid0
modprobe raid1
mknod /dev/md1 b 9 1
mknod /dev/md2 b 9 2
mknod /dev/md3 b 9 3
mknod /dev/md4 b 9 4
mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm --create --verbose /dev/md2 --level=0 --raid-devices=2 /dev/sda3 /dev/sdb3
mdadm --create --verbose /dev/md3 --level=1 --raid-devices=2 /dev/sda5 /dev/sdb5
mdadm --create --verbose /dev/md4 --level=1 --raid-devices=2 /dev/sda6 /dev/sdb6
mdadm --detail --scan >> /etc/mdadm.conf
swapon /dev/md2
mount /dev/md3 /mnt/gentoo
mkdir /mnt/gentoo/boot
mount /dev/md1 /mnt/gentoo/boot
mkdir /mnt/gentoo/home
mount /dev/md4 /mnt/gentoo/home
mount -t proc none /mnt/gentoo/proc
mount -o bind /dev/ /mnt/gentoo/dev
chroot /mnt/gentoo /bin/bash
env-update
source /etc/profile