Some new Xbox One key features have been revealed at PAX Australia. Aside from the usual "3X's the computing power" offered by the Cloud service, Microsoft have now stated that the cloud essentially gives you an "unlimited sized" hard drive, allowing players to save unlimited game data via the service.
Xbox Live offers Xbox One unlimited storage space in the cloud for all Xbox Live members to store numerous types of Xbox Live content, including your profile, games, Achievements and entertainment. This content is stored and saved in the cloud so you can automatically access it anywhere, anytime, no matter where you are.
Source: Examiner