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

On 20 May 2021, Leslie Rhorer outgrape:

On 5/19/2021 3:01 PM, antlists wrote:

quoted

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.