Commonly-used command lines for my home backups:
ssync –update-only –no-sync-meta –no-detach –src-path /Volumes/homes/mail/ –dst-path /Volumes/Hotwired/Backups/Mail/
or:
rsync -rv –size-only /Volumes/homes/mail/ /Volumes/Hotwired/Backups/Mail/
rsync -rv –size-only /Volumes/disk\ 1/Pictures/Photos/ /Volumes/Hotwired/Backups/Pictures/Photos/
(see also cdrecord and hdiutil for a couple of incantations to burn the resulting filesystem)