Re: RAID0 Set-up?

[Alan Chandler <alan@chandlerfamily.org.uk>]

On Monday 11 September 2006 19:35, Gary Catalano wrote:
> Anyone have experience setting up RAID on Debian Testing etch-3 (or
> something similar?)  I'm having a bear of a time.

I did it, but you have to do a few things which are not straight forward.

This is approximately how I did it assuming two partitions on each disk, the 
first a 32M /boot partition, the rest all raid (I actually had a raid root 
partition of 4G and the rest of the disk as a raided lvm2 volume)

If you already have a running system on one of the disks that you will 
ultimately be in the raid setup you have to add a few more steps.  You should 
be able to work out from below exactly what they are

You need to get your raid arrays up and running using mdadm, something like 
the following, which creates a partial array

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hdb1 missing
mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/hdb2 missing


or similar.  Repeat for all raid devices you need

mount /dev/md1 /target
mount /dev/md0 /target/boot


then you need to add the output from 

mdadm --examine --scan 

into /etc/mdadm/mdadm.conf

then look at /etc/default/mdadm and set the parameters in there.  In 
particular define if you need the raid arrays setup in initrd, so that you 
can have a raid array as root.

now you need to update the initramfs to include the raid startup

update-initramfs

also edit /boot/grub/menu.lst to specify /dev/md1 as the root device 

now we will need to copy the existing root to raid

mkfs -t ext2 /dev/md0
mkfs -t whatever-u-want /dev/md1

mkdir /target
mount /target /dev/md1

mkdir /target/boot
mount /target/boot /dev/md0

rsync -axHq / /target
rysnc -axHq /boot /target/boot


now edit /target/etc/fstab to adjust mount points for the new raid arrays


Now install grub in the boot sectors of both hard drives

This bit I am not 100% certain of - I think it goes like this

grub-install /dev/hda
grub install --root-directory=/target /dev/hdb

Now reboot - but select  /dev/md1 as your root device - you can do that from 
the grub menu but not chosing the selections from the list but selecting e 

finally you need to start using /dev/hda in your raid array

first use fdisk or cfdisk to set the partition types of /dev/hda1 
and /dev/hda2 to raid. (type fd)

then

mdadm --add /dev/md0 /dev/hda1
mdamd --add /dev/md1 /dev/hda2

(note I think you may have to confirm that you are not making a mistake in the 
above two steps)

I then repeat the 

mdadm --examine --scan
update-initramfs

replacing the array definitions in there with the new ones and then updating 
the initrd with them - although I think there ought to be no difference.  




-- 
Alan Chandler
http://www.chandlerfamily.org.uk