Density is the whole story
A traditional enterprise rack draws a few kilowatts. A modern GPU rack can draw many times that, and the newest rack-scale systems are widely described as drawing well over 100 kW per rack. Every watt becomes heat that has to be removed, and the amount you can remove from a single rack with air alone has a practical ceiling.
Where air cooling runs out
Air-cooled halls are commonly designed around a modest number of kilowatts per rack. With careful design, such as hot and cold aisle containment and rear-door heat exchangers, that figure can be pushed higher. Beyond a point, though, moving enough air becomes impractical, noisy and inefficient. If a facility was built for lower-density equipment, it may simply not be able to host a dense GPU deployment, however much power it has available.
What liquid cooling means
Liquid cooling is an umbrella term. In direct-to-chip designs, cold plates sit on the processors and carry most of the heat away in liquid, while the rest is handled by air. Rear-door heat exchangers use liquid at the back of the rack. Immersion cooling submerges equipment in fluid. Each has different requirements for plumbing, floor loading, maintenance practices and equipment compatibility, so asking for liquid cooling is not enough. Ask which kind.
Questions to put to a facility
- What rack density is the hall designed for, and what is installed today?
- Which liquid-cooling method is supported, and is it in production or planned?
- What coolant temperatures and flow rates does the design support?
- How is the system maintained, and what is the plan if a loop fails?
- Is the cooling capacity available now, or does it depend on construction still to come?
Retrofit versus purpose-built
Some operators retrofit existing halls for liquid cooling, while others build new capacity designed around it. Retrofits can be faster but may limit density or scale. Purpose-built sites usually handle high density better but may be further from ready. Neither is automatically better. What matters is that the specific hall you will occupy can support your hardware on your schedule, and that you have seen evidence of it.
Match the hardware to the hall
The most expensive mistake is buying dense hardware before confirming where it will live. Check your vendor's cooling requirements first, then find facilities that meet them. Cooling should be a screening criterion at the start of a search, not a surprise at the end.
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