How to make your storage greener

Rick Cook explains how to evaluate your storage energy demands and reduce the cost of power consumption.

What you will learn: Rick Cook explains how to evaluate your storage energy demands and reduce the cost of power consumption.

Since storage accounts for 26% of the overall data center power budget, it's important that storage administrators approach going green with straightforward cost-benefit analysis.

According to the EPA, data centers in 2006 accounted for 1.5% of electricity use in the U.S. and that number may double in the next three years. By adopting existing energy-saving techniques, the agency says, data centers could cut their energy use nearly in half, potentially saving $14 billion by 2011.

The first step when looking at greening your storage is to know how much energy your storage consumes and how much that energy costs. You should be able to get the basic numbers on power consumption and heat production from the makers of your arrays and other equipment. If not, you can measure power consumption yourself.

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To measure the energy consumption of your storage, meter the power consumption of the circuits feeding the storage devices and the air conditioning. Your facilities management people may already be doing this or you may be able to install temporary meters on those circuits. Once you know how much electricity your storage uses (and how much energy cooling the data center uses) the next step is to calculate your costs.

To do that, you will need to know your electric rate. Since commercial electric rates typically include a number of factors, this isn't as easy as multiplying kilowatt hours times a rate. What's more, rate structures vary greatly by utility company. There is no "standard" electric rate for commercial customers.

Almost all electric rates include a basic service charge that you pay whether you use any power or not, and a cost based on the amount of electricity you use. Beyond that is where the variables come in. For example, many electric utilities charge their commercial customers (the class your data center likely falls into), for power consumption on a step basis: so much per kilowatt hour for the first X kilowatts, a higher rate for the next block of kilowatt hours, and so on. In addition, some utilities have different prices depending on the season and the time of day. Others have a ratchet mechanism where the minimum charge is determined in part by the highest monthly consumption in the previous 12 months.

Your electric utility can provide you with the rate information and may even offer assistance in calculating your energy costs, as well as suggesting saving methods. They may also be willing to give you some insight into where energy costs are going in your area.

Look for simple changes you can make which can save energy and reduce cooling loads. For example, changing the filters in your environmental conditioning system more often may save a surprising amount of energy. Putting your data center cooling on a separate zone can also save money by giving you finer control over your cooling load. Consider cutting your total cooling load in the data center by redistributing the air flow to your servers and arrays to make more efficient use of the cooled air. Remember what you're trying to cool is the equipment, not the room. Make sure the flow to the devices isn't obstructed by other equipment.

A related potential savings is plugging air leaks which are bleeding cooled air out of the data center where it is needed and into areas where it isn't. In effect, this means weatherstripping the data center. Another possibility is simply turning off equipment when it's not in use. If you don't need most of your storage arrays during non-work hours you can shut them off to save power.


This was first published in February 2008

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