Why would you want this?

Let’s look at some reasons why. First, the Branch Office Guide states a soft limit of 1200 DCs per domain due to a limitation of FRS. Not that it won’t work, mind you, but that the difficulty of recovering from a disaster with that many or more DCs approaches impossibility… or at least extreme difficulty.

It’s also much faster. FRS replicates the whole file when it changes, while DFS-R only replicates the changed bits. For example, if you have a 5MB file in which the spelling of a single word is changed, with FRS the whole 5MB must be copied. With DFS-R the copy would only be a few KB (I don’t know exactly how much off-hand, but from what I’ve been told it’s quite small).

Migrating to DFS-R is done in four stages: Start, Prepared, Redirected, and Eliminated.
(The most detailed information is contained here:
sysvol-migration-series-part-1-introduction-to-the-sysvol-migration-process.aspx
sysvol-migration-series-part-2-dfsrmig-exe-the-sysvol-migration-tool.aspx
sysvol-migration-series-part-3-migrating-to-the-prepared-state.aspx
sysvol-migration-series-part-4-migrating-to-the-redirected-state.aspx
sysvol-migration-series-part-5-migrating-to-the-eliminated-state.aspx