This back up device is used by me to back up a web server.
The software used is Retrospect. Retrospect creates a folder on the drive and copies all of the selected data over to the folder. When you choose to do the backup, or when it is scheduled to, if will check the files in the folder and match them to what is on the server. If the files are different on the server then it will copy them into the folder and take out the previous version.

The performance of the hard drive is excellent. It takes about 2 minutes to complete the back-up which is staggering considering the size of the server. It can do about a quarter of a GB in that time. But obviously your computer will need to be quick as well to get the most out of the speed on the hard drive.

This hard drive isn't cheap but its good value for money when you look at what you are buying.

It is very very strong. It is made from aluminum which is very light weight but very strong and has been dropped a few times by me and not damaged it at all. It also comes in a black protective case which can be seen in the picture. You can fit all the stuff you need in there like the drive itself, the transfer cable and any back up schedules you may have.

I have also found out that is can stand heat. This was left in the glove box in my car over the weekend once and it was a very hot weekend, about 26 degrees out and would have been much hotter in there and there was nothing wrong with it after.

This is well worth the money, never fails and works wonders with retrospect.
If you don't need as much space then there are other devices out there for less money but they won't give you the protection as this one does.