In a perfect world, you easily could rein in the rapidly increasing amount of power that storage systems consume just by telling users to stop stockpiling data. In the real world, you'd lose your job for suggesting that.

Luckily, you have a number of more realistic options to help reduce the energy required to power your systems. Storage isn't the biggest energy hog in the data centre, but cutting back on storage's power consumption can lower the energy bill significantly and free up precious energy for other uses. In addition, saving power by using storage space more efficiently can cut down on wasted capacity, which means spending less on storage in the long run.

For some organisations, moving to energy-efficient storage isn't just a nice, green idea but an essential part of using less power, which in some circumstances has become an extremely limited resource.

Such is the case for the San Diego Supercomputer Center (SDSC). "In the last few years, SDSC has added hundreds of researchers and their data collections... which brought online many more servers, another petabyte of spinning storage, and a major power upgrade in 2006, and another planned for 2008," says Don Thorp, manager of operations with SDSC. Moving to energy-efficient storage "wasn't visionary insight as much as the cold shock of reality. The growth in storage is not slowing; our ability to add power is very limited."

To reduce the energy consumed by data storage, an enterprise must stop thinking of storage as a potentially endless resource. Then it will seek new ways to use fewer, more efficient systems, one analyst says.

"Are you putting out more storage to make up for the lack in performance?" asks Greg Schulz, founder of analysis firm StorageIO Group. "Consolidate. Instead of having two storage arrays, could I do that work with one array, but increase the performance and reduce the response time to make end users happy, plus use less power?"

Powering down storage systems

There are several approaches to achieving storage efficiency. At SDSC, Thorp looked to Copan Systems, one of a handful of relatively new, smaller vendors attempting to reduce storage power consumption. He reports a 10 to 20 percent reduction in storage power consumption since switching to Copan Systems last July.

Copan Systems uses the Massive Array of Idle Disks (MAID) architecture for storing long-term, persistent data, which typically comprises 80 to 90 percent of an enterprise's overall data, says Aloke Guha, Copan Systems' CTO. A MAID system houses a large number of drives, the majority of which usually are powered off. The system powers on only the disks that store data requested by a certain application, so enterprises use their storage more efficiently and save on energy.

"Online transactional systems are expensive, high-end disk space, with lots of disks running and caching and with that comes a lot of power consumption," Guha says. "With MAID, when the disks are powered off, there's not as much vibration; they don't generate as much heat." A Copan Systems cabinet can have as many as 896 drives, but only 25 percent of those are powered, he says.

Pillar Data Systems, a specialty storage vendor founded in 2001, has optimised its storage-system software for the use of Serial Advanced Technology Attachment drives, because they are more energy efficient than Fibre Channel, says company spokesman Christopher Drago. Pillar Data also combines storage resources from network-attached storage and storage-area network environments to save on space and gain efficiencies in management, power and cooling, he says.

Pillar Data's efforts have proved worthwhile for Michael Geldart, senior manager of computer operations at Cubist Pharmaceuticals in Lexington, Mass. Three years ago, he set out to design and build a revamped data centre to support the company's 450 users, taking energy and cooling efficiency into consideration. At that time he replaced EMC storage with a Pillar Data system that offered 24 times the amount of storage capacity and decreased power usage by 3 to 4 percent, he says. "The green factor was in the back of my mind [when choosing Pillar]," Geldart says.

Compellent Technologies and Nexsan Technologies also are young companies attacking the power-consumption problem. Well-established storage players, including Dell, EMC, HP and IBM are tackling the problem, too, but the start-ups are behind the innovation in this area, StorageIO's Shultz says. The bigger players are getting their product stories lined up, directing customers toward consolidation and an evolutionary approach to energy efficiency.

EMC, for example, says enterprises should identify data that isn't accessed actively and move it to secondary storage; reduce or eliminate data duplication so that if a file is stored more than once, only one copy is saved but the pointers to it are maintained; and remove duplicate blocks of data in a file. It sells tools to help with these goals.

The data-centre power situation "is a crisis for some . . . but for the most part it's a manageable problem," says Mark Greenlaw, senior director of storage product marketing at EMC. "But I also don't see it going away."