On Thu, 23 Feb 2012 08:47:27 +0000 "J. Ali Harlow" [off-list ref] wrote:

On Thu, Feb 23, 2012, at 09:34 AM, Jes Sorensen wrote:

quoted

On 02/23/12 02:57, John Robinson wrote:

quoted

On 22/02/2012 23:16, Jes Sorensen wrote:
[...]

quoted

The goal was to try and reduce the number of bug reports over this by
making it more obvious/explicit, so if you have a suggestion for how to
do so in a better way, I am all game.

How about:

mdadm /dev/md0 --add %s
: %s was already a member of /dev/md0, attempting re-add
: Re-add failed because <reason>
: Not performing add as that would zero the superblock on %s and make it
a spare
: mdadm --add used to do that automatically but it was potentially
dangerous
: If that is what you really want to do, use mdadm --zero-superblock %s
first.

This would get my vote, way better than my messy attempt.

Would
: If %s doesn't hold any useful data, use "mdadm --zero-superblock %s"
before adding.
be a further refinement?

Maybe .. though "useful" seems a bit of a .... soft(?) word.  What exactly
does it mean in this context?
I would probably prefer something like "If you are happy to discard the data
on .....".

And in the earlier suggestion with have "<reason>" which would certainly be
good to have, but filling in the details is not straight forward
unfortunately.

I'm happy to take patches .... they don't have to be perfect, just an
improvement on what we currently have is enough.

NeilBrown