Microsoft has recently released confirmation that the multiplayer for Halo 4 will require either a flash drive or hard drive with 8 GB of free space. The company “highly recommends” using a hard drive in order for the “best experience”.
However, if you own an Arcade, Core, or 4 GB Xbox 360 model, you’ll have to invest in a flash drive to compensate for the small storage space. In this case, Microsoft recommends investing in one of the official Xbox 360 flash drives supplied by the company. You can use other flash drives, but they need to be configured in the same way that the official ones are.