Re: Zeroing multiple superblocks

[Bill Davidsen <davidsen@tmr.com>]

Neil Brown wrote:
> On Mon, 25 Jan 2010 10:52:21 +0100
> Andre Noll <maan@systemlinux.org> wrote:
>
>   
>> On 15:09, Jim Paris wrote:
>>
>>     
>>> I guess the only way to be fully safe with the current approach is to
>>> do a zero-superblock over and over until it complains.
>>>       
>> mdadm --zero-superblock tries to guess the location of the superblock.
>> If more than one superblock is found, the one with the latest creation
>> time is being zeroed. So yes, the method you describe works and I think
>> it is the most reliable way to remove all superblocks of a device.
>>
>> Maybe we could teach mdadm --zero-superblock to honor the --metadata=x
>> option which would zero-out the region of the device where the
>> version-x superblock is located.
>>     
>
> Latest mdadm has this feature.
> And if --metadata= isn't given, it repeatedly trying to find and zero a
> superblock until no more superblocks can be found.
>   

That would be potentially a bad thing, people do run things like RAID1+5 
and might want to clear on block and save the other, still possibly part 
of a running array, one. I'm not sure that's a safe default behavior.

-- 
Bill Davidsen <davidsen@tmr.com>
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein