IBM Z Door Is a Model of Sustainable Design By John Buscemi Sometimes a door is just a door. And sometimes it’s a paradigm for a different way of thinking. Take, for example, the front door of the IBM z15, the latest version of the IBM Z mainframe. At first glance, it appears solid. But it actually hides a multi-layered system of aluminum and acoustic foam shapes, designed to do something crucial for a computer in a modern data center: increase airflow to cool the machine, while also reducing noise. Sometimes a door is just a door.