Re: Deleting mdadm RAID arrays

[Bill Davidsen <davidsen@tmr.com>]

Marcin Krol wrote:
> Thursday 07 February 2008 22:35:45 Bill Davidsen napisał(a):
>   
>>> As you may remember, I have configured udev to associate /dev/d_* devices with
>>> serial numbers (to keep them from changing depending on boot module loading 
>>> sequence). 
>>>       
>
>   
>> Why do you care? 
>>     
>
> Because /dev/sd* devices get swapped randomly depending on boot module insertion
> sequence, as I explained earlier.
>
>   
So there's no functional problem, just cosmetic?
>> If you are using UUID for all the arrays and mounts  
>> does this buy you anything? 
>>     
>
> This is exactly what is not clear for me: what is it that identifies drive/partition as part of 
> the array? /dev/sd name? UUID as part of superblock? /dev/d_n?
>
> If it's UUID I should be safe regardless of /dev/sd* designation? Yes or no?
>
>   
Yes, absolutely.
>> And more to the point, the first time a  
>> drive fails and you replace it, will it cause you a problem? Require 
>> maintaining the serial to name data manually?
>>     
>
> That's not the problem. I just want my array to be intact.
>
>   
>> I miss the benefit of forcing this instead of just building the 
>> information at boot time and dropping it in a file.
>>     
>
> I would prefer that, too - if it worked. I was getting both arrays messed 
> up randomly on boot. "messed up" in the sense of arrays being composed
> of different /dev/sd devices.
>
>   
Different devices? Or just different names for the same devices? I 
assume just the names change, and I still don't see why you care... 
subtle beyond my understanding.
>   
>>> And I made *damn* sure I zeroed all the superblocks before reassembling 
>>> the arrays. Yet it still shows the old partitions on those arrays!
>>>   
>>>       
>> As I noted before, you said you had these on whole devices before, did 
>> you zero the superblocks on the whole devices or the partitions? From 
>> what I read, it was the partitions.
>>     
>
> I tried it both ways actually (rebuilt arrays a few times, just udev didn't want
> to associate WD-serialnumber-part1 as /dev/d_1p1 as it was told, it still claimed
> it was /dev/d_1). 
>   

I'm not talking about building the array, but zeroing the superblocks. 
Did you use the partition name, /dev/sdb1, when you ran mdadm with 
"zero-super" or did you zero the whole device, /dev/sdb, which is what 
you were using when you first built the array with whole devices. If you 
didn't zero the superblock for the whole device it may explain why a 
superblock is still found.

-- 
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 



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