How the Synchronization Works

There are some nice improvements in offline files between XP’s implementation and
Vista’s. First, Vista uses a new and faster algorithm to ascertain which files/directories
are different between the server and client. Second, Vista uses a process called Bitmap
Differential Transfer to sync changes. To understand this and the benefits, you must first
know that in XP the entire file (if changed) was copied back to the server. However,
with Bitmap Differential Transfer only the specific blocks that have been modified while
offline (disconnected from the server) are sent up to the server. This allows for faster
synchronization of only modified data.
Along with performance improvements as a result, Vista can now handle larger files
such as .PST and .MDB files (unlike X P, which could not). In Vista, no file types are excluded.

Keep in mind that Bitmap Differential Transfer works only from the Vista client up to
the server. In synchronizing the other way, from server to client, the entire file is sent.
Among the other great changes is that Vista synchronizes only the current user logged
in (unlike X P, which tried to sync all the users of the machine) and you can also script
your synchronization using WMI.