I've been using a Squeak-based backup program every night for the last
5 years.  It's called Banyan and has just been updated to version 1.2.

1.2 is updated to run on Squeak 4.3, a couple of new conveniences and
a safe handling of Squeak's limitation on large files (that it cannot
determine their modificationTime or size).

See SqueakMap for installation.  Also, since SqueakSource is no longer
accepting new projects, this is also my first foray into using
SqueakSource3.