Power savings on a platter: How to save on storage

After servers, the biggest area of focus for energy efficiency in your data center should be storage. Storage is increasing in power density. As you go from gigabytes to terabytes it gets hotter. The increase in power density for data center storage didn't spike as servers did a few years ago, but it's still significant. A fully loaded storage frame from EMC can consume as much as 700 watts per square foot, or about 2.1 KW per rack, according to EMC.

While storage density per drive has increased, the actual number of drive spindles per bay and power consumption per spindle hasn't gone up much. "We've had a gradual increase in the number of spindles that can fit into a storage frame but it's nowhere near the change you saw for servers," says Dick Sullivan, director of enterprise marketing at EMC.

1. Refresh old storage.

Dramatic increases in drive storage densities mean IT can consolidate into fewer storage frames and save a considerable amount of electricity. A user who moves 1 terabyte of Fibre Channel storage from 73 gigabyte drives to a single 1 terabyte spindle will cut power use by about 94%, Sullivan says.

The disk drives themselves are also somewhat more efficient than they were just a few years ago. Automated power management features that can spin down disks, virtual LUNs, and variable speed cooling fans are some of the technologies that can help IT manage storage for greater efficiency, Sullivan says.

2. Add serial ATA, Flash drives to the mix.

Fibre Channel disk drives are the most power hungry. Spindle for spindle, a SATA drive uses 28% less power than a similar FiberChanel unit, but they're slower and offer lower performance. Combining SATA with flash drives can compensate for that while saving power. Sullivan expects storage frames to gradually migrate to a combination of Fibre Channel, SATA and flash drives. Eventually, he predicts, Fibre Channel will go away entirely.

Flash cuts energy costs while improving overall performance. Byte for byte, flash uses 38% less energy than Fibre Channel drives while increasing the input/output operations per second (IOPs) to power ratio by 98%.

So what does that mean? Consider a 65TB storage frame consisting of 528 146 GByte 15,000 rpm Fibre Channel disk drives. Replacing those with a storage frame containing eight 200GB flash disks, 104 400 Gbyte 10,000 rpm Fibre Channel drives and 32 1 terabyte SATA drives would reduce power by 32% and storage costs by 17%, Sullivan says.

There's just one problem: Up to now allocating data between those three types of storage has been a manual process. EMC, like other storage vendors, has been working on developing automated "storage tiering" tools. Sullivan says storage administrators can expect to see new products that automate the movement of data some time in 2010.

Ultimately, Fibre Channel is on its way out, says Sullivan. "I don't think it's too far in the future when we'll have storage systems with no Fibre Channel, SSDs for performance and 1 terabyte, 2 terabyte and 5 terabyte SATA drives," he says.

3. Consolidate your data.

Finally, a sure-fire way to gain efficiencies is to invest in deduplication, compression and archiving technologies, which can substantially reduce overall storage capacity requirements. "Going through consolidation can cut energy consumed by a storage system from one third to one half," Sullivan says.

Related Content:

• Four ways to save energy - and $$$ - in legacy data centers
• Fans: The new power hogs in the data center.
• Data center density hits the wall
• Why data center temperatures have moderated

Robert L. Mitchell writes technology-focused features for Computerworld. Follow Rob on Twitter at http://twitter.com/rmitch, send e-mail to rmitchell@computerworld.com or subscribe to his RSS feed.