[mythtv-users] OT Help: mdadm segfault

[George Mari]

Steve MacLaren wrote:
> On 9/17/07, John Drescher <drescherjm at gmail.com> wrote:
>>>  Unfortunately, I don't get very far trying to diagnose with mdadm - it
>>> simply complains that /dev/md0 does not exist whether booted from the
>> live
>>> CD or not...
>>>
>> If it is actually running this is good. Do you have a /dev/md0 node?
>>
>> ls -l /dev/md*
>>
>> If not
>>
>> cd /dev
>> MAKEDEV md
>>
>> Then try
>>
>> mdadm --assemble --scan
>>
>> or if you know all the drives
>>
>> mdadm --assemble /dev/md0 <drives>
>>
>>
>> /dev/md exists (it is an empty directory)
> 
> mdadm --assemble /dev/md0 <drives> results in:
> "mdadm: error opening md0: no such file or directory"
> 
> so then I tried MAKEDEV md anyway; I got:
> "udev active, devices will be created in /dev/.static/dev"
> 
> forging ahead, I did
> mdadm --assemble /dev/.static/dev/md0 <drives>, and
> "mdadm: no recognizable superblock on /dev/sda"
> "mdadm: /dev/sda has no superblock - assembly aborted"
> 
> Sadly, I got the same "/dev/sd* has no superblock" regardless of which drive
> I put first in the list.  So all 4 drives failed simultaneously?
> 
> 
Don't lose hope - a few months ago I was able to recover a 6-drive RAID5 
array that had 2 drive failures.  You're not supposed to be able to do 
that, and I am no RAID expert - just patient, and did the research.

Please post the output of each of the following:

mdadm --examine /dev/sda1
mdadm --examine /dev/sdb1
mdadm --examine /dev/sdc1
mdadm --examine /dev/sdd1

I'm guessing that /dev/sda1 will report no valid info or some such, but 
if the other 3 drives all have same/similar values for the 'events' 
field, you should be able to recover.

Here are a couple of links that helped through by recent failure:

http://www.mail-archive.com/linux-raid@vger.kernel.org/msg07815.html

http://www.linuxquestions.org/questions/showthread.php?p=2557045#post2557045