Backup external hard drive to another external hard drive

[sswats]

I'm trying to help someone backup their iPhoto library.
They have a MacBook Air with 128GB storage. The iPhoto library is over 90GB and the MacBook doesn't even boot now.

I moved the iPhoto library to an external drive and pointed iPhoto to it and it works fine.

But question is, how do I setup a backup of that external drive to another external drive.
Time machine doesn't backup external drives.

System has to be as automated as possible as they are not too computer savvy.

 

[ChocolateStarfishRammer]

You'd likely need some third party software. Give google a shout.

 

[bloodiedathame]

SuperDuper, Carbon Copy Cloner.

 

[shine]

I use SuperDuper to back up external drives and clone my boot drive to another external drive. IMHO it is worth every penny.