Re: Ubuntu - RAID Array not "assembling" on boot.

["John Reeves" <john.reeves@mailc.net>]

On Tue, 21 Nov 2006 21:13:00 +0100, "Henrik Holst"
<henrik.holst@idgmail.se> said:
> > Having a great deal of difficulty getting my 3 disk RAID 5 array to
> > reappear on restart, Ubuntu 6.10.  
... < snip > ...
> > the only way I can get
> > the RAID Array to assemble is to issue the following:
> > 
> > mknod -m 0660 /dev/md0 b 9 0
> > mdadm --assemble /dev/md0 /dev/sda1 /dev/sdb1 /dev/sdc1

> Try "dpkg-reconfigure mdadm" as root. Under Debian this will give you
> the chance to configure the startup configuration for all software raids
> in the system. Under any cirtumstances you should not have to use mknod.
> Instead try adding the --auto=yes switch to mdadm. Then mdadm will
> create the node itself.

That's the one!  Blowing away my current mdadm.conf and issuing a
dpkg-reconfigure mdadm bought my raid online with the subsequent reboot
- I am very greatful!  Now I guess I would like to know where I go wrong
:)

I created the raid in the first place by issuing a:

# sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 \
/dev/sda1 /dev/sdb1 /dev/sdc1

After this, no mdadm.conf file was created for me, so I made by own by
issuing:

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

And thats when the whole "assemble" on boot problem came from.  I
presume that the above command (--detail --scan)  is not the correct way
to make the mdadm.conf file - how should it be made?

Finally, on a side note, I have formatted this array (/dev/md0) with
ext3, I planned to exapand the array in the future by adding extra disks
- I presume I can do this with 'mdadm --grow' (and some extra research!
:)  Am I correct on this assumption?

Thanks again
John.