According to the Production Blog of Kojima Studios, Metal Gear Solid: Peace Walker will include an optional data install on the UMD.
The disc will include two options, the first being a small install at 300MB while the full install is 800MB. This is said to make the load times much faster and the action run more smoothly.
Metal Gear Solid: Peace Walker will be released in Japan tomorrow via PSN and retail sources. The game will be released in Europe and the US later in the year.
Thanks, Just PushStart