Apple’s been selling the iPad Camera Connection Kit for copying multimedia content directly from digital cameras and with the latest hack surfaced on the web, the Camera Connection Kit will allow users to access data from the external HDD as well. To make this work, you need to have a jailbroken iPad without which the mod is not possible. Few other things needed are a split USB to power the external drive (a normal USB cable is fine if the drive supports external power source) and a terminal to SSH into iPad.
The mod seems daunting but Maxwell Shay has put out a good guide for you to do it successfully. Check out the video proof below.