Data Center Management: Keep your hot side hot & your cold side cold

I think it was the mid 80's when McDonald's advertised the "McDLT" (I loved that music). The claim to fame for this 'burger' was the packaging.  It was all about separation by temperature.  The hot meat separated from the cold and delicate lettuce to be joined sometime later by the consumer. At that point, my burger purchase to consumption delta t was about 5 seconds, and I didn't really benefit from the separation. I never bought one...

25 years later, I look at a customer data center and I say "you need to keep your hot side hot and your cold side cold". Then, I inexplicably (to the customer) chuckle. The stuff we remember...

But, I was correct - you really do want to keep them separate.  I started digging around on the Internet and I found this is a good method for data center efficiency - It is a solid intellectual discussion of the benefits.

I do not advocate anybody's solution, but the benefits of separation seem obvious.

Separating your hot and cold air streams optimizes your use of cooling and fan energy. Separation also makes it possible to adopt all kinds of cool (pun intended) energy saving alternatives.

With the hot and cold streams separated, it becomes possible to:

  • Inject cool outside ambient air in to the hot stream - free cooling
  • Completely vent hot to the outside and pull outside air into the chillers ( that may not need to do any chilling much of the year)
  • Use that heat to make living space warmer - supplement heat plant for office space
  • Use available coolants like water to pre-chill the hot stream and so many more.

Lastly, it is relatively easy to achieve. The barrier need not be perfect; heavy plastic curtain can be a cheap resource to isolate the air flows (think freezer sections in some groceries).

Virtually every customer I speak with knocks on the door of power, space, or cooling constraints.  Hot aisle/cold aisle separation can go a long way to reduce the cooling problem. Fortunately, I also have a solution to the power and space problem! I'll save that for my next post!