How green is your data centre? If you don't care now, you will soon. Most data centre managers haven't noticed the steady rise in electricity costs, since they don't usually see those bills. But they do see the symptoms of surging power demands.

High-density servers are creating hot spots in data centres that have surpassed 30 kilowatts per rack for some high-end systems. As a result, some data centre managers are finding that they can't get enough power distributed out to those racks on the floor. Still others are finding that they can't get more power to the building: they've maxed out the power utility's ability to deliver additional capacity to that location.

The problem already has Mallory Forbes' attention. "Every year, as we revise our standards, the power requirements seem to go up," says Forbes, senior vice president and manager of mainframe technology at US-based Regions Financial. "It creates a big challenge in managing the data centre because you continually have to add power."

Energy efficiency savings can add up. A watt saved in data centre power consumption saves at least a watt in cooling. IT managers who take the long view are already paying attention to the return on investment associated with acquiring more energy-efficient equipment. "Energy becomes important in making a business case that goes out five years," says Robert Yale, principal of technical operations at US-based The Vanguard Group. His 5600-square-metre data centre caters mostly to Web-based transactions. While security and availability come first, he says Vanguard is "focusing more on the energy issue than we have in the past".

Green data centres don't just save energy, they also reduce the need for expensive infrastructure upgrades to deal with increased power and cooling demands. Some organizations are also starting to take the next step and are looking at the entire data centre from an environmental perspective.

Following these steps will keep astute data centre managers ahead of the game.

Consolidate your servers, and consolidate some more

Existing data centres can achieve substantial savings by making just a few basic changes, and consolidating servers is a good place to start, says Ken Brill, founder and executive director of US-based consultancy The Uptime Institute. The Uptime Institute has studied this issue for several years. In many data centres, Brill says, "between 10 percent and 30 percent of servers are dead and could be turned off".

Cost savings from removing physical servers can add up quickly - up to $US1200 in energy costs per server per year, according to one estimate. "For a server, you'll save $US300 to $US600 each year in direct energy costs. You'll save another $US300 to $US600 a year in cooling costs," says Mark Bramfitt, senior program manager in customer energy management at Pacific Gas & Electric (PG&E). The US-based utility offers a "virtualization incentive" program that pays $US150 to $US300 per server removed from service as a result of a server consolidation project.

Once idle servers have been removed, data centre managers should consider moving as many server-based applications as feasible into virtual machines. That allows IT to substantially reduce the number of physical servers required while increasing the utilization levels of remaining servers.

Most physical servers today run at about 10 percent to 15 percent utilization. Since an idle server can consume as much as 30 percent of the energy it consumes at peak utilization, you get more bang for your energy dollar by increasing utilization levels, says Balkansky.

To that end, VMware is working on a new feature associated with its Distributed Resource Scheduler that will dynamically allocate workloads between physical servers that are treated as a single resource pool. Distributed Power Management will "squeeze virtual machines on as few physical machines as possible", Balkansky says, and then automatically power down servers that are not being used. The system makes adjustments dynamically as workloads change. In this way, workloads might be consolidated in the evening during off-hours, and then reallocated across more physical machines in the morning, as activity increases.

Turn on power management

Although power management tools are available, administrators today don't always make use of them. "In a typical data centre, the electricity usage hardly varies at all, but the IT load varies by a factor of three or more. That tells you that we're not properly implementing power management," says Amory Lovins, chairman and chief scientist at the Rocky Mountain Institute, a US-based energy and sustainability research firm.

Just taking full advantage of power management features and turning off unused servers can cut data centre energy requirements by about 20 percent, he adds.

That's not happening in many data centres today because administrators focus almost exclusively on uptime and performance, and IT staffers aren't comfortable yet with available power management tools, says Christian Belady, distinguished technologist at Hewlett-Packard. He argues that turning on power management can actually increase reliability and uptime by reducing stresses on data centre power and cooling systems.

Vendors could also do more to facilitate the use of power management capabilities, says Brent Kerby, Opteron product manager at Advanced Micro Devices' server team. While AMD and other chip makers are implementing new power management features, "in Microsoft Windows, support is inherent, but you have to adjust the power scheme to take advantage of it", he says. Kerby says that should be turned on by default. "Power management technology is not leveraged as much as it should be," he adds.