A data storage system with a parallel array of dense memory cards and high airflow is described. In one example, a rack-mount enclosure has a horizontal plane board with memory connectors and external interfaces. Memory cards each have a connector to connect to a respective memory connector of the horizontal plane board, each memory card extending parallel to each other memory card from the front of the enclosure and extending orthogonally from the first side of the horizontal plane board. A power supply proximate the rear of the enclosure and the first side of the horizontal plane board provides power to the memory cards through the memory card connectors and has a fan to pull air from the front of the enclosure between the memory cards and to push air out the rear of the enclosure.