Data Centers are Refrigerators

At their simplest level, data centers are refrigerators.  There are walls, a ceiling and floor, multiple racks, a couple doors and anything hot inside gets cooled.

How you lay out the contents of a refrigerator is determined by the manufacturer.  Similarly, how you lay out the contents of a data center is often determined by the architect and/or Mechanical, Electrical and Plumbing (MEP) firm.

Changes to your refrigerator layout are generally rarely performed, and when they do happen you take anecdotal measures for success (i.e.:  did the milk spoil quickly, did the soda freeze.)

We advise clients to be a bit more analytical when making changes in the air cooled data centers.  Some organizations have IP-based temperature probes throughout the data center, providing a precise view of the data center.   Often, we see less sophisticated organizations making layout changes to extend the data center life without much more than a “hope” the changes are positive.

What’s a simple way to measure the impact of changes?

We advocate use of a simple temperature strip attached to the input (cold aisle) side of racks:

This will immediately give a visual indication of inlet temperature, in a simple unobtrusive manner.

Ready to make changes?

A simple Post-it can be used for recording temps before, and then after changes.  Record the starting point, and once the room stabilizes (in a matter of an hour), record the ending point. 

We believe in KISS (Keep It Simple, Stupid).  Metrics are a must, and even a simple approach is preferred over no approach.  While we do believe a number of data center managers can use their body as a thermometer, a bit more science is generally preferred.

How hot should the data center be in practice?  64-81 °F or 18-27 °C ambient temperature, according to TIA/ANSI standard 942.  At the limits, there can be issues (freezing in direct expansion air conditioning under 68°F or increased device fan noise approaching 81°F.)  In a hot aisle/cold aisle orientation, the hot aisle can be significantly warmer (it’s called the “hot aisle” for a reason) without issue to the equipment.

So why do some data center managers keep it cool?   Often fear.  If a computer room air conditioning unit fails or is taken offline for maintenance, the air flow (distribution) may be insufficient.  Paying attention to the design intention of the space is imperative when making changes and accommodating maintenance.

With appropriate air distribution, data center managers can raise the ambient temperature of the data center and realize lower cooling costs.