Ubuntu - RAID Array not "assembling" on boot.

Ubuntu - RAID Array not "assembling" on boot.

[John Reeves]

Hey,

Having a great deal of difficulty getting my 3 disk RAID 5 array to
reappear on restart, Ubuntu 6.10.  Here's the contents of my
/etc/mdadm/mdadm.conf file:

ARRAY /dev/md0 level=raid5 num-devices=3
UUID=6a9a102a:101addd2:f95758f6:11ac6d3c 

Obviously /dev/md0 does not "appear" on restart, 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

I can add these lines to my /etc/init.d/bootmisc.sh which does work, but
seeing as I'm not 100% sure what the mknod command is doing, and the
fact that I'm pretty sure that this is not the way it's mean to be... 
(the mknod is required, or mdadm complains that /dev/md0 does not
exist).  

I'm nearly tearing my hair out over this one, so if someone could be of
assistance I would be greatly appreciative.

Regards
J. Reeves.

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

[Henrik Holst]

John Reeves wrote:
> Hey,
> 
> Having a great deal of difficulty getting my 3 disk RAID 5 array to
> reappear on restart, Ubuntu 6.10.  Here's the contents of my
> /etc/mdadm/mdadm.conf file:
> 
> ARRAY /dev/md0 level=raid5 num-devices=3
> UUID=6a9a102a:101addd2:f95758f6:11ac6d3c 
> 
> Obviously /dev/md0 does not "appear" on restart, 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
> 
> I can add these lines to my /etc/init.d/bootmisc.sh which does work, but
> seeing as I'm not 100% sure what the mknod command is doing, and the
> fact that I'm pretty sure that this is not the way it's mean to be... 
> (the mknod is required, or mdadm complains that /dev/md0 does not
> exist).  
> 
> I'm nearly tearing my hair out over this one, so if someone could be of
> assistance I would be greatly appreciative.

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.

/Henrik Holst

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

[dean gaudet]

On Tue, 21 Nov 2006, John Reeves wrote:

> Hey,
> 
> Having a great deal of difficulty getting my 3 disk RAID 5 array to
> reappear on restart, Ubuntu 6.10.  Here's the contents of my
> /etc/mdadm/mdadm.conf file:
> 
> ARRAY /dev/md0 level=raid5 num-devices=3
> UUID=6a9a102a:101addd2:f95758f6:11ac6d3c 

just to be sure... that's one line in your config file and your mailer 
wrapped it?

also -- do you have a "DEVICE partitions" line in the config file?

-dean

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

[John Reeves]

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.

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

[dean gaudet]

On Tue, 21 Nov 2006, John Reeves wrote:

> 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?

that's fine, but you need a "DEVICE partitions" line as well... that's 
what i suspect your problem was.  dpkg-reconfigure probably created it for 
you.  you should look -- because if it put in a "DEVICE /dev/sda1 
/dev/sdb1 /dev/sdc1" line then you really want to change it to 
"partitions"... so that it can handle device renames properly.


> 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?

yep.

-dean

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

[Gabor Gombas]

On Tue, Nov 21, 2006 at 10:26:35PM +0000, John Reeves wrote:

> # 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?

It's correct, but as was already said it is not enough. On Debian you
can use the /usr/share/mdadm/mkconf script that spits out a complete
mdadm.conf.

Gabor

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     MTA SZTAKI Computer and Automation Research Institute
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