Data Preservation

If i have 2 NT servers ( pdc , bdc )is there any easy way to make sure that data on one is copied or mirrored on the other?
I am looking for a DFS type of a solution.
I want the backup server to pick up the workload at once and for it to be extremely reliable.
second priority is load balancing – is there any way to put it into the fallover solution?
both servers are nt 4 sp6.
Please give a description or point to an article ora book.
( note: I have heard that dfs in nt 4 really does not work? )