How To Speak Data Center: Power vs. Energy
October 26, 2012
The data center facilities clique can be difficult to break into for IT. It's a maze of jargon as complex as that of networking or storage. Many IT professionals have been boxed in, out-maneuvered or just plain pwn3d by physical data center issues. But IT needs to understand data center issues, and how to communicate with the facilities team, to ensure that IT equipment gets the power and cooling it needs and that IT can address management's questions about current and future capacity requirements. Over several posts I'll share a few rules to help you shed the n00b moniker and build your credibility inside the data center.
IT pros typically don't have backgrounds in electrical or mechanical engineering, which makes it difficult to ask the right questions when it comes to issues such as power and cooling. Many IT professionals believe these issues aren't complicated, and they overestimate their own depth of understanding. That can cause problems.
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We've all heard (or made) quips about dumb users. From a data center facilities perspective, an IT person that doesn't understand the difference between 120v and 208v power is just another dumb user. Whether you talk with your own facilities staff, outsourced facilities staff, collocation staff, or a contractor, being able to speak the language of the data center will vastly improve your ability to get what you need and help you develop a good working relationship with the facilities staff.
During the last 20 years, I have identified a few data center concepts to be important to IT. One is the difference between power and energy. In a casual conversation, people might use the two terms interchangeably. But power and energy mean two very different things to engineers. Power is the instantaneous measurement of the use of electricity; think of a 100-watt light bulb. Energy is power use over a period of time; that 100-watt bulb being lit for one hour. Power can be thought of the rate at which energy can expended. Energy is the total quantity of work performed.
When I teach IT professionals, I compare this to 1 Gbit per second vs. 1 Gbyte of storage. IT professionals typically don't confuse network bandwidth with storage capacity; the differences are ingrained in their thinking. But the casual and seemingly interchangeable use of power and energy can lead to confusion and misunderstanding.
For instance, more than one IT manager has been burned because he or she estimated the data center load (how much power the data center needs every moment) by using energy data. For example, the bill from the electric company is expressed in kilowatt hours, or the energy consumed over the entire month. But the electric bill doesn't tell you the data center load. You might be able to use the numbers in the bill to figure out the data center load, but you won't find it printed on the paper.
Thus, the first step in breaking the data center code is to be clear and specific when using the terms power and energy. The correct use of these terms will build your credibility with engineers and facilities staff, and ensure that IT will be accurate in its measurements. Take the time to check whether you use these terms correctly. If you make a mistake, take it as an opportunity to learn. Even experienced facility people can benefit from this exercise.
Ken Miller is data center architect with the IT Infrastructure and Operation Services division of Midwest ISO, developing mission-critical facilities.