Why is there 3 discs in LA Noire

The game is huge and each character uses a new technology that was designed to emulate true facial movements and near perfect lip syncing to match the other parts of the face associated with each word and reaction. Every character is played by an actor and the motion capture technology used almost 100 cameras on each actor's face to capture many common reactions and thousands of lines of dialogue in the game. This amounts to tens of thousands of camera captures. As well as LA being so precise in geometry and geography, the models, textures, music and voice audio amounts to a very large portion of the game.