The Xbox 360’s hard drive was removable, allowing owners to replace smaller sized hard drives with larger ones. The unit, however, won’t have a removable hard drive.
The system will ship with a 500 GB drive, but considering the fact that you’ll install all your games onto the drive, it’s probably going to be easy to run out of room.
To help compensate, Xbox One will support external storage drives through the system’s USB 3.0 ports. Essentially, you can pick up a 2 TB external drive, connect it to the system, and install your games onto the external drive. Truth be told, it’d probably be cheaper to buy a larger external drive than the eventual larger drive Microsoft themselves will offer.