There are products out there that take it one step further by
storing the data in "Chunks" rather than files, and storing only
one copy of each chunk. They us an algorithm on the clients to describe
the chunks, and claim excellent performance.
I've been to a presentation from Avamar, but don't know anyone using
it, so I don't know about reliability or performance.
http://www.avamar.com/

Doug Thorneycroft
County Sanitation Districts of Los Angeles County
(562) 699-7411 Ext. 1058
FAX (562) 699-6756
dthorneycroft AT lacsd DOT org