Western Digital Labs seem to have taken the RPi under its wings with this clever approach. It marries the Berry Boot multi boot approach with a 2.5 in HDD that is supposedly optimised for use with the RPi. In the photo, you can see the disk in its WD Labs case and the clever connecting lead that comes with it. This lead provides both power to the disk and to the RPi.
If you’ve not used Berry Boot before, it is a very clever idea. Download the Berry Boot zip file, and follow the instructions to get it onto your micro SD Card, in the usual way.
When you boot the RPi for the first time, you are given the option of installing one or more of the usual RPi distros, ie Raspian, OpenElec etc, but the clever part is that these are installed onto the Hard Disk Drive.
I have two RPis running in this way, one using a WD Labs 1TB HDD and the other a standard WD 2TB portable drive, in use mainly with Open Elec. Both have given sterling service for a year or more.