snap is a tool for the management of UFS2 snapshots created
by mount(8). It can maintain hourly, daily and weekly snap-
shots while trying to minimize the disk space occupied. The
snapshots created are labeled with their creation time, and
users can create them manually.

The major advantage over sysutils/freebsd-snapshot is that
it uses hardlink to save diskspace, mark each snapshot with
its creation time and calculates redundancy in a smart way.

WWW:	http://www.cs.nctu.edu.tw/