According to Rockstar, for Xbox 360,the game will ship on two discs: Disc 1 will be used for a one-time mandatory install and Disc 2 will be used to play the game. After the install, players will be able to play the game and its online competent without any need to switch discs.
This initial install will require an Xbox 360 Hard Drive or an external 16GB USB flash drive with at least 8 GB of free space. The US must be USB 2.0 with a minimum 15mb/s read speed and formatted for Xbox 360 use.
If you want to test your USB flash drive's speed. USBDeview, USBDeview x64
Rockstar recommends using a new USB flash drive “to ensure optimuim performance"
This initial install will require an Xbox 360 Hard Drive or an external 16GB USB flash drive with at least 8 GB of free space. The US must be USB 2.0 with a minimum 15mb/s read speed and formatted for Xbox 360 use.
If you want to test your USB flash drive's speed. USBDeview, USBDeview x64
Rockstar recommends using a new USB flash drive “to ensure optimuim performance"