[clug-talk] mdadm raid 5

[Gustin Johnson]

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Chris R. Thompson wrote:
> Hello,
> 
>    I am configuring an Ubuntu 9.04 Desktop with 4 disks; the primary is a single disk where the O/S resides. The other 3 I am trying to configure in a software raid 5. To do this I am using mdadm; the problem I am having is that post configuration using cfdisk and the mdadm --create command, I restart, and the OS tries to boot from the raid 5, rather then the single disk. I am then stuck into the (initramfs) prompt and forced to repair by uninstalling mdadm.
>     I am of the impression that the /boot is actually modified when installing and configuring the mdadm.

It shouldn't be unless you plan on booting from the array.  When I setup
my array at home I did not modify anything in boot.  My system at home
is running Ubuntu 8.04 server and I just built it a week ago so this is
all still fresh.

>     The question at this point, is where do I need to configure the "boot" option; and what would it be. The technical details are below.
>     single disk is /dev/sda1

In the /etc/fstab I would use the UUID to define the / (root), this goes
the same for /boot/grub/menu/lst (in other words, use the UUID instead
of the device name).

All boot options are likely in /boot/grub/menu.lst unless you
specifically requested LILO or some other boot loader for some strange
reason.

>     raid array 5
>     /dev/sdb1
>     /dev/sdc2
>     /dev/sdd2
>     the /etc/mdadm/mdadm.conf
>     DEVICE partitions
>             ARRAY /dev/md0
>             level=raid5
>             num-devices=3
>             metadata=00.90 spares=0
>             UUID=275d06f7:703df9fd:baf54294:a0156108
>             MAILADDR root
> 
I use this howto as a template:
http://www.gagme.com/greg/linux/raid-lvm.php

It is pretty straightforward and easy to follow.

Hth,
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