direction criterium for synchronisation raid1

[Christina Braun <braun@mail.informatik.uni-essen.de>]

Hello,
which is in raid1 the criterion for the direction of synchronisation? In 
case of  disk-replacing
or removing one mirror-leg (working actual on the other leg ) and add 
the same removed leg later, which has the old data now, again to the mirror?

How can I tell the system which mirrored partition is  now the 
data-source without
making the raid1 new or zero the superblock?  Is the  destination in 
every case the device
in mdadm manage after the add ? Can I see the source or destination by a 
info like mdstat or superblock?
 
I cannot find the  answers of this simple questions. It works by 
testing, but I feel better about my production-system and a later 
replace  if I know it. The found examples describes only the replace of  
ascending order second drives.

Thank You,
Christina