Holger Parplies wrote:
  

I'm not sure why you would need any other format change - and if you had
a tool to reconstruct the pool links you could switch back if you wanted -
at some cost in time and CPU.
      

Here we are back at the original problem. If you have a tool to do that, you
can also copy a pool without handling hardlinks and then re-establish them
(yes, I know, supposing you have enough space). And that *is* feasible right
now, it just comes at a significant cost, because you need to hash and link
every single file in every pc/ directory. For small amounts of data, you won't
mind doing that, but then, for small amounts of data, you don't need to,
because 'rsync -H'/'cp -d' will simply work.
    

But because of the nature of the problem, rsync and cp can't do a small 
piece at a time - and their views of the inodes in question are only 
valid as long as none change before the run completes.  A tool that 
relinks individual files can plug away at it for as long as it takes - 
although I suppose it has to be aware of the nightly run. You probably 
have the whole blackout window with not much else to do anyway.