Yes, you can backup your whole PS3 on an external hard drive through USB... or can even use a flash drive if u dont have that many data to backup and you have a super high capacity flash drive (i think they are just surpassing 64 GB and its like $200[external goes for under $50])
...but there are special procedures (none too difficult) to make it compatible to the PS3...
but i take it with your question that u have never done that huh...it's a shame...
if anything, game saves (not game data) are only .05 MB (.00005 GB) and can be copied/saved on the cheapest flash drive and/or save it onto another ps3 account on ur ps3...
