Leon Woestenberg wrote:

In first instance we were searching for ways to tell mdadm what we
know about the array (through mdadm.conf) but from all advice we got
we have to take the 'usual' non-syncing-recreate approach.

We will try to make disk clones first. Will dd suffice or do I need
something more fancy that maybe copes with source drive read errors in
a better fashion? 

Yes to both. dd will be fine in most cases, and I suggest using noerror 
to continue after errors, and oflag=direct just for performance. You 
could use ddrescue, it supposedly copes better with errors, although I 
don't know details.

-- 
bill davidsen [off-list ref]
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979