Re: My superblocks have gone missing, can't reassemble raid5

[Leslie Rhorer <lesrhorer@att.net>]

On 5/19/2021 11:41 AM, antlists wrote:
> On 19/05/2021 15:48, Leslie Rhorer wrote:
>>      Then I would try recreating the RAID based upon the earlier 
>> Examine report:
>>
>> mdadm -C -f -n 3 -l 5 -e 1.2 -c 512 -p ls /dev/md99 /dev/loop2 
>> /dev/loop0 /dev/loop1
>>
>>      You may notice some of the command switches are defaults.  
>> Remember what I said about a belt and suspenders?  Personally, in such 
>> a case I would not rely on defaults.
> 
> Because defaults change?

	That is one reason, yes.  It also means no mater what else, I know what 
the system is being told to do.

>>      Now try running a check on the assembled array:
>> fsck /dev/md99
>>
>>      If that fails, shutdown the array with
>>
>> mdadm -S /dev/md99
>>
>>      and then try creating the array with a different drive order. 
>> There are only two other possible permutations of three disks.  If 
>> none of those work, you have some more serious problems.
> 
> And here you are oversimplifying the problem immensely.

	No, I am not.

> If those three 
> drives aren't the originals, then the chances are HIGH that a simple 
> re-assembly/creation is going to fail your simplistic scenario.

	Absolutely.  So what?  If it does, very little time and no data 
whatsoever is lost.  If it doesn't fail, then his problem is solved with 
very little trouble.  I have been troubleshooting technical issues for 
well over 50 years, and one of the very first lessons I learned is one 
should try the simplest solutions first.  Whenever they work, they can 
save a tremendous amount of time and effort.  After that, it's time to 
dig out the heavy tools.