Re: Any hope for a 27 disk RAID6+1HS array with four disks reporting "No md superblock detected"?

[Bill Davidsen <davidsen@tmr.com>]

Thomas J. Baker wrote:
> On Thu, 2009-02-05 at 13:49 -0500, Bill Davidsen wrote:
>   
>> Thomas J. Baker wrote:
>>     
>>> The array was made probably two years ago and had been working fine
>>> until recently. In reading the documentation for mdadm, it did seem like
>>> it should have required me to use the higher version but it never
>>> complained when I made it and worked fine.
>>>   
>>>       
>> What have you changed lately? Are the drives all on a single controller? 
>> Are you using PARTITIONS in mdadm.conf and letting mdadm find things for 
>> itself?
>>
>>     
>
> The array is made up of two Dell PowerVault 220s in split bus
> configuration with two Adaptec 39160 Dual Channel SCSI controllers. Each
> half of each PowerVault (7 disks) is connected to one of the channels on
> the Adaptecs. Four channels in all.
>
> As far as changing things, what do you mean? The cause of the failure is
> likely heat as we've had some AC issues recently.
>
>   
Well that's change, but if you can read the drives at all it doesn't 
sound like the typical "fall down dead" heat issues, I would expect tons 
of hardware errors at a lower level from the device controller. Did you 
check the partition tables with fdisk or similar?  Are the drives all in 
the same physical box? IBM split their boxes, running four drives off 
one power and four (or three+CD) off the other. They are likely to have 
something in common, if you can find it you might fix it.

> I didn't use mdadm.conf at all. All disks are partitioned with one
> 'Linux raid autodetect' partition.  mdadm had always found the array
> automatically at boot.
>   

No kernel update or utilities update lately?

Given the choice of identify in hopes of a fixable problem or reinstall, 
config, recover from backup, I'm trying to see if you can do the former 
in preference to the latter.

-- 
Bill Davidsen <davidsen@tmr.com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark