Looking for a Unix file backup system

[Herbert J. Bernstein]

New York University is looking for a solid way to ensure
file integrity under Unix.  If anyone has a good package
for file backup on an active system, an inexpensive but
solid optical disk backup system, a live disk shadowing system,
an automatic mass-store migration system, etc., please send
a mail message to yaya at nyu.arpa, or put up a note on net.unix.
Thanks. - H. J. Bernstein