Halo: The Master Chief Collection will require a hefty day-one update for anyone purchasing the game on disc. The collection will take up most of the space on its Blu-ray disc, which amounts to around 45GB. However, this includes only the campagin modes of each game, with the multiplayer and some other features requiring a 20GB install, according to a Microsoft statement to Kotaku:
Full story from the WPCentral blog...