The Importance of Air Flow Management

In my last article for DCQ we learned a quick and cost effective way to directing the air to the front of the rack. Decreasing the by-pass air in a cold aisle by using directional perforated tiles can increase the effectiveness of the air supplied by 70%. In this edition, I want to address another simple-to-solve issue: Airflow Management.

Some time ago I was touring a company’s (not a Compass customer) data center in the Phoenix area.   As I was walking, I was impressed how clean everything was, how tidy everything looked, etc. It was monstrous facility – very impressive. After seeing the infrastructure support areas, we headed to one of the data halls. The transition from outside the data hall to the raised floor was a nice relief – it felt good and cool after walking outside for what it seemed like 5 miles (a couple of hundred feet) in the Phoenix summer heat.

As the tour guide continued to talk about the features of the data hall and how important PUE was for them I noticed a couple rows of slotted tiles installed in the perimeter of the data hall. These tiles did not have IT equipment or cabinets around them. “That looks odd – maybe they are going to put some cabinets there” – I told myself. I had to ask – so I did. To my surprise the answer was: “We have those there just to make it feel cooler for people when they tour. We have about 3 tours a day.” I guess they willing to trade a lower PUE for cooler tour participants.

Whether it’s your computing gear or the comfort of your visitors, the placement of your perforated tiles is critical for achieving your objectives. Let me explain. A Compass data center provides 1.2 MW of critical IT load power. During Level 5 commissioning, we use a total of 300, 25% perforated tiles. The tiles are arranged simulating a hot aisle/cold aisle configuration. After commissioning is complete, and the Uptime Institute finishes their Tier III Constructed Facility certification testing, we turn over the site to the customer. In this case, we also turned control of the data center operations to the customer because they wanted to operate their own facility. After a few months the customer was ramping power slower than they expected. In turn, they were noticing some fluctuations in the data hall environment and decided to give us a call. In assessing the issue we noticed an unexpectedly high PUE with only 10% of IT load being utilized. We then started to ask some questions regarding the data hall configuration and learned that all 300 of the perforated tiles used in commissioning where still installed. As a result, they weren’t just cooling their rack-mounted equipment they were cooling the entirety of the space. After this quick review, we determined they weren’t expecting any major tours any time in the near future so our recommendation was to decrease or cover the perforated tiles installed that were not providing cooling to IT equipment. The results were immediate – as shown in the following graph below:

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This simple modification enabled the to customer regain control of their data hall environment at their PUE decreased dramatically. As a plus, they have also not received any complaints from tour participants.

The lesson here is simple. When you have a raised floor environment, ensure that the perforated tiles used are ONLY used to cool the IT equipment installed. Then, as your load increases, add the perforated tiles in front of the corresponding cabinet as needed. Seems like a no brainer, but you would be surprised how many data centers I have toured that do not follow this simple best practice.

If you don’t have enough solid tiles to replace the perforated ones, then block the air with a product like the PerfBlock so that your efficiency is not penalized.

open-perf

Open perforated tiles

perf-blocks

PerfBlocks installed

cabinetEmpty cabinet row with PerfBlocks installed to control air flow

 

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