Backup

I am running Ubuntu 12.04 LTS. I have two external USB hard drives. I copy my pictures to one of the USB hard drives to keep as a copy. Since I take a lot of family pictures I need to be able to copy only the new pictures from one of the two hard drives to the other one without doing it manually which I know how to do. Is there an utility you can recommend me that will accomplish this task in the new LTS version. I had a GUI utility which I downloaded from your Ubuntu software center that did this for me without any problems but since I upgraded from 10.04 to 12.04, I lost it and I do not remember the name of it. I believe this is called a differential backup. Can you please help me?. Thank you.