Western Digital My Book 8TB and My Passport 4TB External HDDs Review Western Digital has a number of direct-attached storage (DAS) products based on hard drives. They cater to different market segments. These DAS units usually employ a USB port to connect to the host (Thunderbolt is also popular in the high-end market). Within the USB storage bridge market segment, Western Digital has a number of product lines tuned to specific use-cases. For example, the My Passport product line focuses on striking a balance between capacity and portability, while the My Book targets a 'desktop' use-case with external power, but much higher capacity. Today, we will be taking a look at the 2016 redesign of the My Book and My Passport units.