Xen users - Sep 2007 - domU -->Failure: failed to start /dev/md1

I don''t understand this boot error from the domU:

Begin: Assembling MD array /dev/md1 ...
md: md1 stopped.
mdadm: no devices found for /dev/md1
Failure: failed to start /dev/md1

dom0 is running on software raid. The domU image is a fresh 
debootstraped etch.

/etc/xen/xen-etch.cfg
...
root    = ''/dev/sda1 ro''

disk    = [ ''file:/vd/domains/xen-etch/disk.img,sda1,w'', 
file:/vd/domains/xen-etch/swap.img,sda2,w'' ]
...


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On Sat, Sep 01, 2007 at 08:46:23PM +0200, Frank wrote:
> I don''t understand this boot error from the domU:
> 
> Begin: Assembling MD array /dev/md1 ...
> md: md1 stopped.
> mdadm: no devices found for /dev/md1
> Failure: failed to start /dev/md1
Why does your domU try to assemble a software RAID at all if..
> disk    = [ ''file:/vd/domains/xen-etch/disk.img,sda1,w'', 
> file:/vd/domains/xen-etch/swap.img,sda2,w'' ]
..it only has one block device?

Is this a showstopper for you or does it carry on to boot normally?

Do you have an /etc/mdadm/mdadm.conf in the domU?

Does your domU have mdadm set to run and assemble arrays?

Cheers,
Andy


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Andy Smith schrieb:
> On Sat, Sep 01, 2007 at 08:46:23PM +0200, Frank wrote:
>> I don''t understand this boot error from the domU:
>>
>> Begin: Assembling MD array /dev/md1 ...
>> md: md1 stopped.
>> mdadm: no devices found for /dev/md1
>> Failure: failed to start /dev/md1
> 
> Why does your domU try to assemble a software RAID at all if..
That''s what I wounder about
> 
>> disk    = [
''file:/vd/domains/xen-etch/disk.img,sda1,w'',
>> file:/vd/domains/xen-etch/swap.img,sda2,w'' ]
> 
> ..it only has one block device?
only this one which is configured.
> 
> Is this a showstopper for you or does it carry on to boot normally?
It carrys on normaly.
> 
> Do you have an /etc/mdadm/mdadm.conf in the domU?
No and of cause nothing installed like this.
> 
> Does your domU have mdadm set to run and assemble arrays?
> I don''t know but that I would not know. How can I figure it out?
> Cheers,
> Andy
> 
> 
> ------------------------------------------------------------------------
> 
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Hi,

On Sat, Sep 01, 2007 at 09:49:01PM +0200, Frank wrote:
> Andy Smith schrieb:
> >Is this a showstopper for you or does it carry on to boot normally?
> It carrys on normaly.
So I wouldn''t really worry.  No wonder it can''t start a RAID
array
if you don''t have one.  You might want to look into blacklisting the
RAID modules in your domU, and/or disabling mdadm.

Cheers,
Andy


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Andy Smith wrote:
> On Sat, Sep 01, 2007 at 08:46:23PM +0200, Frank wrote:
>   
>> I don''t understand this boot error from the domU:
>>
>> Begin: Assembling MD array /dev/md1 ...
>> md: md1 stopped.
>> mdadm: no devices found for /dev/md1
>> Failure: failed to start /dev/md1
>>     
>
> Why does your domU try to assemble a software RAID at all if..
>
>   
>> disk    = [
''file:/vd/domains/xen-etch/disk.img,sda1,w'',
>> file:/vd/domains/xen-etch/swap.img,sda2,w'' ]
>>     
>
> ..it only has one block device?
>
> Is this a showstopper for you or does it carry on to boot normally?
>
> Do you have an /etc/mdadm/mdadm.conf in the domU?
>
> Does your domU have mdadm set to run and assemble arrays?
>
> Cheers,
> Andy
>   
Is there *ANY* reason to do software RAID, LVM, or other filesystem 
cuteness in a DomU? Except maybe for configuration testing purposes? Let 
the Dom0 do the work, I''m quite certain it will be more efficient about
it.

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Nico Kadel-Garcia schrieb:
> Andy Smith wrote:
>> On Sat, Sep 01, 2007 at 08:46:23PM +0200, Frank wrote:
>>  
>>> I don''t understand this boot error from the domU:
>>>
>>> Begin: Assembling MD array /dev/md1 ...
>>> md: md1 stopped.
>>> mdadm: no devices found for /dev/md1
>>> Failure: failed to start /dev/md1
>>>     
>>
>> Why does your domU try to assemble a software RAID at all if..
>>
>>  
>>> disk    = [
''file:/vd/domains/xen-etch/disk.img,sda1,w'',
>>> file:/vd/domains/xen-etch/swap.img,sda2,w'' ]
>>>     
>>
>> ..it only has one block device?
>>
>> Is this a showstopper for you or does it carry on to boot normally?
>>
>> Do you have an /etc/mdadm/mdadm.conf in the domU?
>>
>> Does your domU have mdadm set to run and assemble arrays?
>>
>> Cheers,
>> Andy
>>   
> Is there *ANY* reason to do software RAID, LVM, or other filesystem 
> cuteness in a DomU? Except maybe for configuration testing purposes? Let 
> the Dom0 do the work, I''m quite certain it will be more efficient
about it.
> 
No there is no reason and I don''t want, need and understand not why I 
get this error. I''m not trying to use software raid in a domU. That 
woult be funy as this strange error I get. Software raid is only used in 
dom0, only there!

My question is: Why I get this error in the domU if I don''t use
software
raid in the domU and how can I get rid off this errors?

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Hi,

On Sat, Sep 01, 2007 at 09:51:38PM +0100, Nico Kadel-Garcia
wrote:
> Is there *ANY* reason to do software RAID, LVM, or other filesystem 
> cuteness in a DomU? Except maybe for configuration testing purposes? Let 
> the Dom0 do the work, I''m quite certain it will be more efficient
about it.
I generally agree, although I have some customers who want to manage
their own filesystems with LVM, so for them I give them one block
device with / on and another with nothing on for them to use as an
LVM PV as they please.  So that ends up as LVM on LVM on RAID.  I''m
sure there''s a performance hit but haven''t benchmarked exactly
how
much.

It also has the advantage that when they want more disk space I can
attach another block device and they can add this to their VG
without having to reboot their domU.

Cheers,
Andy


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Andy Smith wrote:
> Hi,
>
> On Sat, Sep 01, 2007 at 09:51:38PM +0100, Nico Kadel-Garcia wrote:
>   
>> Is there *ANY* reason to do software RAID, LVM, or other filesystem 
>> cuteness in a DomU? Except maybe for configuration testing purposes?
Let
>> the Dom0 do the work, I''m quite certain it will be more
efficient about it.
>>     
>
> I generally agree, although I have some customers who want to manage
> their own filesystems with LVM, so for them I give them one block
> device with / on and another with nothing on for them to use as an
> LVM PV as they please.  So that ends up as LVM on LVM on RAID. 
I''m
> sure there''s a performance hit but haven''t benchmarked
exactly how
> much.
>
> It also has the advantage that when they want more disk space I can
> attach another block device and they can add this to their VG
> without having to reboot their domU.
>   
Hmm. OK, avoiding rebooting is useful. I''ve just found running LVM 
inside of LVM to be very awkward to gain access to the file systems form 
Dom0, and make snapshotting the DomU filesystem for off-line backup to 
be even riskier.

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