Backing up Graphic Files

I work intensively with graphics.  My hard drive on my laptop is too small to hold my stash.  I put all of the graphics on a 1T Passport.  Is there a way that I can synchronize this Passport with a second Passport so that the files are continuously backed up?  I can’t afford to lose all of this work.  Any ideas will be appreciated.

You didn’t mention what OS you use. Microsoft has Sync Toy it’s free. Windows 7 has Sync Center built in. I’ve never used them. I have GoodSync it’s paid. You definitely want more than one drive to hold the data. The forum is full of post where people moved everything to one external drive to freeupo space then had some disaster.