[RAID Install] Can't install Grub - SOLVED

Question

Me & a friend are building a local serveur on Arch (32-bit) for ~10 PCs in our association (half of them allready having AL Wink )
This server will basically have 2 main fonctions :
- NFS/YP server for a few PCs we've built under Arch for young people here
- backing up a few PCs we're using for the association.
Machine is HP with a PIV 1.7GHz, 512Mb SDRAM for now, & a single HDD IDE controller.
We got two UDMA 160GB HDD (Hitachi ) as we planned right from the start to improve on data security (& speed when possible).
I've set up partition as following :
- hda1 & hdb1, 100 Mb both, raid-1 for /boot
- hda2 & hdb2, 2 Gb both, raid-1 for swap
- hda3 & hdb3, 10 Gb both, raid-1 for /
- hda4 & hdb4, 150 Gb both, raid-1 + LVM2
Now I'm setting up Arch 0.7.2-20061104 (latest ISO from tpowa Smile ) , & everything went allright up to the point I wanna install the bootloader (might be the 10th time I set up AL this year)
To do so I'm following "Install Grub on the Primary Hard Drive (and save the RAID config)" (wich I may edit if I succeed this raid setup) with a look on "Reinstalling GRUB" both on the wiki.
1st I'm not 100% sure about mkinitcpio.conf config when it comes to raid; I've added 'raid' to HOOKS + a line just like on "Configuring mkinitpcio" :
Code:
md=2,/dev/hda3,/dev/hdb3
Edited grub/menu.lst, installed the kernel... but I want to chroot in order to install Grub I can't mount /dev :
Code:
# mount -o bind   /dev      /mnt/dev
keeps complaining about wrong fs type.
I chrooted anyway and launched grub :
grub> root (hd0,<TAB>
Error 21: Selected disk does not exist
I'm purely stuck here with no idea about what went wrong
If someone has spare time & knowledge, it'd be very nice indeed (our schedule says we begin to play with the network services 2morrow
EDIT : corrected the mkinitpcio.conf "md=2" line.

Answer 1

About install gub, I got it thanks to warnaud :
/dev/mdN was unexistent until I launched
# makedevs
Thereafter grub found the disk :
# grub
grub> root (hd0,0)
grub> setup (hd0)
grub> quit
"save the RAID config" was allready done at this point.
Guess I misconfigured something in mkinitcpio.conf / menu.lst, 'cause when I boot it says :
:: Running Hook [raid]
:: Running Hook [filesystems]
:: Loading root filesystem module...-e
Attempting to create root device '/dev/md2'
ERROR: Failed to parse bloc device name for '/dev/md2'
    unknown
ERROR: root fs cannot be detected.
Kernel panic...
mkinitcpio misconfiguration maybe.
From wiki :
First add the raid hook to the HOOKS list in /etc/mkinitcpio.conf
OK :
HOOKS="base udev autodetect ide raid filesystems"
Add some Kernel Parameters is less clear, or it maybe after reading "Installing_with_Software_RAID_or_LVM" that says to list the devices in the ROOT array ?
Kernel Parameters: Specify all your md arrays with md= parameter: (only adding the raid array you're booting from is enough)
add the following to the kernel line in grub/menu.lst:
Example: md=0,/dev/sda3,/dev/sda4 md=1,/dev/hda1,/dev/hdb1
working example: kernel /vmlinuz26beyond root=/dev/md0 ro md=0,/dev/sda1,/dev/sdb1
So should one list its / or its /boot array ?