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

[Nix <nix@esperi.org.uk>]

On 20 May 2021, Leslie Rhorer outgrape:

> On 5/19/2021 3:01 PM, antlists wrote:
>> Yes you can explicitly specify everything, and get mdadm to recover the array if the superblocks have been lost, but it's nowhere
>> as simple as "there are only three possible combinations".
>
> 	The number of permutations of the order of three drives is precisely six.  The permutations are:
>
> 1, 2, 3
>
> 1, 3, 2
>
> 2, 1, 3
>
> 2, 3, 1
>
> 3, 1, 2
>
> 3, 2, 1
>
> 	The Examine stated it was 2, 3, 1, but the device order is not
> at all unlikely to have changed. Once again, I was very explicit in
> saying the simple create may not work and if not he is facing some
> much more serious issues. That was and is in no way incorrect. The
> odds one of them will work are not terrible, and if so, he is in good
> shape. Are you seriously implying there is no way any of them could
> possibly work?

Of course not, but it's *likely* none will work. mdadm's default chunk
size has probably changed since the array was created if it's more than
a few years old, for starters.