Thermal design supporting Gen 12 hardware: cool, efficient and reliable

This post details the thermal design considerations for Cloudflare's Gen 12 server hardware, focusing on standardization, system layout, and flexibility. Key technical contributions include: defining a thermal specification with requirements for ambient conditions (5-40°C), thermal margins, fan failure support (requiring operation with one fan failure), and power efficiency in cooling; optimizing system layout with larger axial fans (80mm) and Extended Volume Air Cooled (EVAC) heatsinks for improved airflow and heat transfer; and designing for hardware flexibility to support up to 2x single-wide GPU add-in cards. It also discusses rack-level thermal considerations, such as cold/hot aisle management and airflow resistance.