My Book Duo with 20TB of external storage
Prices for the My Book Duo start at $259.99 for 4 terabytes and range up to $849.99 for 20 terabytes. B&H is taking orders for all storage capacities with free expedited shipping and no tax collected outside NY and NJ. Amazon is also accepting backorders.
Source: Western Digital debuts My Book Duo with up to 20TB of external storage