Why power consumption is on the rise

New Data Center Strategies Newsletter [1], Network World [2], 2/27/07

One of the most striking changes in data centers has been the increase in power consumption over the past three to five years.

When we looked at consumption per rack, we used to see an average of 1.5 kW to 2 kW. In our data center benchmark in 2006 we measured an average rack consumption of 6 kW. Some organizations define a “standard rack” as one that can support up to 8 kW of equipment draw. With a threefold increase in just three years, many data center managers are beginning to wonder: where does this end?

A study (PDF [3]) by Jonathan Koomey, a staff scientist at Lawrence Berkeley National Laboratory in Berkeley, Calif., showed worldwide data center power consumption has doubled in five years. It now takes five one-gigawatt power plants just to power the servers in the U.S.

The increase in power consumption is not driven by consumption per CPU as much as by the increase in the number of servers. In our benchmark we found that servers were increasing 11% per year, even during a period of aggressive server consolidation and virtualization. With compound growth rates like those, it is not surprising that power use has doubled in five years. The trend, in fact, is likely to continue for the next five years at least.

Even worse, Koomey’s study only counted servers. In our research we have seen storage growing at an average rate of 75% per year. In a number of industries, such as financial services and healthcare, average storage growth (in gigabytes) was exceeding 100% per year. Even though smaller hard drives can deliver larger capacity, this level of growth still indicates a net increase in the number of hard drives. The rotational speed of hard drives is also increasing, from 3,600 RPM five years ago to 15,000 RPM in many drives today. Since rotational speed is directly related to power consumption, storage growth and higher RPM mean rapidly increasing power consumption for storage too.

The good news is that since power consumption has now become a challenge, vendors are attempting to competitively differentiate on power consumption. CPU manufacturers, server and power supply manufacturers and hard drive manufacturers are all publishing power consumption estimates and competing on that front. Meanwhile, technologies such as virtualization (see “Combining approaches for power savings” [4]) and MAID (see “Power savings for storage” [5]) are creating opportunities for smarter use of existing resources and a corresponding reduction in power consumption.

If you are building a new data center, or managing an existing site, you need to factor power consumption into your cost forecasts. That means using published power ratings in purchasing decisions as well as reflecting these costs back to the business units if you have chargeback schemes. After all, you don’t want to end up losing all the benefits of Moore’s Law every time you get the electricity bill.

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