To make it more clear, are you looking just for backup some files/data or the whole entire volume(s) ?
Also do you want to backup the system or replicate it ? ( replicate is like taking an exact copy of all your system ).

Do you want to backup snapshots, or the real data ? also the backed up data, is it from the kind that used all the time, or there are some period of time that files (data) are not in use, and you may use the backup time in this period of time ?