I will focus on each subject more in detail in future blogs, but in this blog I would like to cover a set of overall trends. Those readers who follow my blogs may not find a lot that’s new, but I do have new information about each of the following:
- Carbon regulations’ impacts on data centers
- Metrics (PUE and DCeP)
- Variable speed/frequency drive (VSD/VFD)
- New ASHRAE operating ranges for datacom equipment
- Air flow management and airside economizer
- Linking cooling equipment
Carbon regulations’ impacts: The current U.S. House of Representatives’ cap-and-trade bill does not single out data centers for controlling their greenhouse gas (GHG) emissions. The U.K.’s carbon reduction commitment (CRC) goes beyond that. This was covered in my previous blog. Zahl Limbuwala of the British Computer Society gave a good overview of CRC and pointed out some of its problems. Regardless of its shortcomings, CRC will go into effect in April 2010 and will impact the U.S. companies conducting business in the U.K. Note that CRC is the most advanced (or restrictive) regulation in the world and currently applies to the U.K. only.
Data center metrics: There is no question that PUE is the dominant metric in use for data center efficiency, although several shortcomings have been reported. In some sessions, a few counterexamples were given (i.e., bad PUE numbers are actually energy efficient and good PUE numbers are energy inefficient). A noteworthy piece of news is that EPA is extending its Energy Star program to data centers and plans to publish the specification in January 2010. Another is the development of the data center energy productivity (DCeP) metric. Ultimately, it is the IT output per watt that is the most important measure. However, it is very hard to implement, and eight proxy metrics (to simulate closely) are being considered in place of it, as shown here. Emerson’s Energy Logic is one of the proxy candidates, and it was discussed in DRT’s seminar.
Emerson’s Energy Logic Metric
Variable speed/frequency drive (VSD/VFD): There is no reason to keep the cooling motor running at 100% capacity all the time. Depending on the current air condition, you can flexibly control its capacity. Power is proportional to the cube of the fan speed. This means if you reduce your fan speed by 50%, you will decrease the power by 88%. This is a big saving and will be tested by a few companies that participate in Silicon Valley Leadership Group’s second annual data center energy summit (last year’s information is here). I am on the planning committee for this year’s summit.
ASHRAE’s new ranges: ASHRAE stands for the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, established to advance technology “to serve humanity and promote a sustainable world.”
ASHRAE has set safe operating ranges (temperature and relative humidity) for datacom equipment but recently updated the ranges. With the new ranges, the restriction on temperature and humidity has been relaxed. This means you can raise the temperature in your data centers to minimize the cooling requirement for servers and other IT equipment. You can increase the chance of using outside air (airside economizer). Jim Smith, CTO of DRT, mentioned that in Santa Clara Valley, he could operate with airside economizer 60% of the time before the range change and 80% of the time after. See DRT’s most recent data center information here.
None of the participants in the DRT seminar, however, have exploited the new range yet. It seems to be hard to be the first one to try out the new range.
Airflow management: Such things as cold/hot aisle containments are common place now. Small things like filling gaps on the raised floor and racks are surprisingly effective at little expense. Air side economizer is known to be very effective, but depending on the design, it cannot be used for retrofitting.
Quoting myself in my previous blog:
“In this building, DRT pumps outside air via air handlers (that is on rooftop) below the raised floor with a fan (along the side of the building)”
What this means is that your roof needs to sustain multiple heavy air handlers and that you need to factor in enough space for air to pass along the side of the building. This is why this design is not necessarily suitable for retrofitting cases.
Another benefit of this is to cut down or eliminate the use of water, which is increasingly recognized as a scarce resource.
Linking cooling equipment for better control: In the past, different cooling devices were operated independently of each other, causing a situation in which one device humidified while others dehumidified on the same floor. This is obviously not very efficient. Connecting all the equipment together for communication yields the most effective cooling. An extension of this is to link both cooling and IT equipment to further control power consumption. This method is known as dynamic power management.
EPA: EPA published the Energy Star specification for servers in May and is now working on Energy Star for storage. In addition, as discussed before, Energy Star for data centers is in progress. Andrew Fanara of EPA touched upon the current cap-and-trade bill in the U.S. (H.R. 2454). According to Fanara, there is only one mention of data centers in the bill, but the bill does not single out data centers. I think, however, data centers will be impacted by this bill because they consume a significant amount of power. His recommendation was to measure and monitor power usage at your data centers.