Drobo is an external storage hardware device developed by Data Robotics. It connects to a computer using USB, FireWire, eSATA, or iSCSI, and allows a user to connect up to four or eight SATA hard drives inside it. In the picture is an example of a Drobo.
What makes the Drobo unique from other solutions is the ease of connecting multiple drives into one external storage device and having any data saved copied across the drives using RAID. Which means even if one of the drives fail you'll still know your data is safe.