WD's line of My Book external hard drives have been around for quite a long time. Today we are checking out their latest My Book Duo drive, which if you can guess by the name features two drives. With two drives you can either run them in RAID-0 mode for super-fast speed, or switch to RAID-1 for redundancy as the drives will mirror each other. The WD My Duo is the perfect thing for someone who is looking for large capacity storage without having to setup a NAS or install drives themselves. This is a USB 3.1 drive so you can connect it to any PC or Mac for easy backups and file sharing. WD is offering this drive in capacities from 4TB all the way up to 20TB. They have sent us the 20TB model so lets see what it can do!