Intuition Doesn't Cut It!

Even after working on green IT projects for the past four years, I keep being amazed how one's intuition is insufficient to fix data center air flow and cooling issues.  I'm reminded that data always needs to be collected and reviewed in order to fix problems.

Recently, I was asked to take a look at a small 1,800 square foot data center running at about 100 watts per square foot.  It contains 29 servers and 6 computer room air conditioners (CRAC).  As data centers go, this is pretty simple.

The problem was that about 20% of the data center is running hot - hot being better than 90 degrees F and 99 degrees F in a few places.  I was asked how many new CRACs should be installed, and where should they be placed.  The question on the surface certainly appeared reasonable - even to me.

I collected information about the data center's environment and reviewed a air flow and temperature model which I sat down and studied.  Nothing really jumped out at me.  The servers running hot were 18 feet in front of a CRAC with nothing between the two.

Then it hit me.  The data center is actually not hot enough!

I looked at all the CRACs and they are all thermostatically controlled and set at 75 degrees F.  One of the CRACs return air was only 73.7 degrees F.  The result?  It was never turning on.  The unit was blowing hot air into the data center.

Now it made sense.  The 74 degree F air was being raised 20 plus degrees by the servers resulting in the 90 degree F and hotter temperatures.  So I thought of a crazy idea.  Why not see what happens if I turn off that one CRAC.

WHOA! The servers cooled down.  Without 5,000 CFM of 74 degree F air being blown around by the CRAC that never got hot enough to turn on to cool its air, the data center actually cooled down.

So, I was asked how to fix a hot-spot problem by spending money and increasing monthly operational costs. I fixed the problem by turning a CRAC off and saving the client about $10,000 in annual maintenance and operating expenses.

The moral of the story?  Base your decisions on facts and measurements and model machine room air flow so you can properly manage it.

Learn more: http://www.virteratech.com