A data center is a facility housing servers and storage systems for data processing. It is the physical backbone of the internet. When you load a webpage, send an email, or stream a video, the work happens in a data center somewhere. These buildings run 24 hours a day, every day.

Data centers require massive amounts of power and cooling. Servers generate heat. Cooling systems keep them from overheating. Some facilities use outside air in cool climates. Others use liquid cooling for high-density racks. Microsoft even experimented with underwater data centers to reduce cooling costs.

Key components

• Servers: the computers that do the work
• Storage: disk arrays and tape libraries
• Networking: routers, switches, fiber connections
• Power: generators, UPS systems, redundant feeds
• Cooling: air conditioning, fans, liquid systems

Data centers are concentrated in a few regions: Northern Virginia, Dublin, Singapore. Land, power, and tax incentives draw them. But they also strain local grids and water supplies. The cloud is not weightless. It has a physical footprint.