great success!

so we improved our synchronization just a bit... first run took 11 minutes, we managed to optimize it a bit and cut it down to 8 minutes.

new solution:

1. grab all users and groups from A
   
2. add missing users to B
   
3. compare existing groups in A and B
   
   1. delete from B those that don't exist in A
      
   2. add the new groups to B (this was previously done in step 4)
4. build a local list of all groups and members in B (this is already done for A in step 1)
   
5. compare users for each group in A and B
   
   1. if they are in A and not B, add to B
      
   2. if they are in B but not A, remove from B

end result: same functionality, still no down-time.

time taken: 10 seconds.