raid1+raid0 mdadm

raid1+raid0 mdadm

[Dariusz Malec]

I can't configure mdadm. I have created 2 raid1 devices and i wanted to 
connect  them with raid0. Everything is fine when i use command line, 
but after reboot mdadm starts only raid1 devices. Where I can find info 
about such config?
Darek

Re: raid1+raid0 mdadm

[Andre Noll]

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On 18:27, Dariusz Malec wrote:

> I can't configure mdadm. I have created 2 raid1 devices and i wanted to 
> connect  them with raid0. Everything is fine when i use command line, 
> but after reboot mdadm starts only raid1 devices.

Are you using udev?

IIRC, there was an issue with stacked md devices like yours. Your
problem might be that the device node for the final raid0 is missing.

If your raid1's are md0 and md1, add

	mknod -m 600 /dev/md2 b 9 2

to your init scripts, just before calling mdadm.

Of course, that's only an ugly workaround (that once worked for me).

Andre 
-- 
The only person who always got his work done by Friday was Robinson Crusoe

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Re: raid1+raid0 mdadm

[Luca Berra]

On Tue, Mar 21, 2006 at 07:00:50PM +0100, Andre Noll wrote:
>On 18:27, Dariusz Malec wrote:
>
>> I can't configure mdadm. I have created 2 raid1 devices and i wanted to 
>> connect  them with raid0. Everything is fine when i use command line, 
>> but after reboot mdadm starts only raid1 devices.
>
>Are you using udev?
>
>IIRC, there was an issue with stacked md devices like yours. Your
>problem might be that the device node for the final raid0 is missing.
>
mdadm --auto=yes creates device files for you.

L.


-- 
Luca Berra -- bluca@comedia.it
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Re: raid1+raid0 mdadm

[Herta Van den Eynde]

Dariusz Malec wrote:
>
>    I can't configure mdadm. I have created 2 raid1 devices and i
> wanted to connect them with raid0. Everything is fine when i use
> command line, but after reboot mdadm starts only raid1 devices.

Not sure if by "mdadm starts only raid1 devices", you're actually 
referring to the output of "cat /proc/mdstat", or to the fact that the 
devices won't mount properly at boottime.

If the latter:  I used to have LABEL references in /etc/fstab, rather 
than actual device names, and that proved impracticable for raid1+0 devices.

Suppose you have two raid1 devices, md0 and md1, with which you create 
raid0 device md2.  You then create an ext2/3 filesystem on md3.
If you dump the header of md2 (# dumpe2fs -h /dev/md2), you will find 
the filesystem label you used when you created the filesystem.  When you 
dump the headers of md0 and md1, you will only see the label on one of 
these devices (as is to be expected give that they are members of the 
md3 *stripeset*).
When you mount using the label, chances are that it will try to mount 
md0 rather than md2.

Changing the LABEL references to actual device names (e.g. /dev/md2) 
solved the issue for me.

Kind regards,

Herta

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