Data Center managers are learning about the inefficiencies of the tile and the costs associated with adding more and more cooling capacity to the data center airflow system. As a result of their pursuit of reducing hot spots and improved cooling, they have developed two, competing, design philosophies. We call these two methods the "River" and the "Lake".
The Lake environment relies on creating a large pool of cold air under the floor and in the cold aisle. This pool, or lake of air, is pressurized under the floor. As the pressure is released through the tile, it is expected to fill the cold aisle. The servers are cooled by the internal fans pulling the cold air from the middle of the aisle through the server.
The River environment, on the other hand, is designed to use the flow of air to cool. It relies on the movement of air to provide a dissipative effect on the servers and through the server fans. The river method treats the Data Center as an ecosystem of airflow. A molecule of cool air leaves the CRAC unit, moves through the under floor plenum, through the tile and directly into the front of the server, cooling the server then retreating through the hot upper plenum back to the CRAC unit.