What does geli attach -a do?

[Christian Baer]

Good evening, folks!

Ok, I know what that does. I can read manpages. :-)

Is the effekt of this somehow documented by numbers though? Basicly
meaning: Does this function 'only' tell me if the data on the provider
is currupt? Or does it help to isolate it or can even restore broken
data (to a point).

If one of the latter ist the case, what are the numbers on this? How
much data (in per cent) may be broken, before no more isolation and/or
restoration is possible?

Does it make sense to use this in combination with a mirror?

Regards
Chris