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Power-smart disk systems

Disk drive systems use more power than just about any other data center gear, but storage vendors are addressing this problem with a variety of technologies.

Disk drive systems use more power than just about any other data center gear, but storage vendors are addressing this problem with a variety of technologies.

By Matt Perkins

Last fall, Adaptec Inc. kicked off its Green Power Initiative by introducing a new capability for many of its RAID controllers called Intelligent Power Management. The product was made available with the company's Series 5 and Series 2 Unified Serial RAID controllers, and was designed to help configure storage systems to reduce power consumption by up to 70% without forfeiting performance.

"What we decided to do was to address the whole storage package," said Suresh Panikar, director of worldwide marketing at Adaptec. "Our initiative said that from now on our products will have a flavor of power management." Storage administrators can configure banks of drives to operate at different power levels at different times, and set the drives to spin up and down according to usage patterns.

Adaptec is one of several storage providers eyeing green initiatives in the data center. Vendors such as Enhance Technology Inc., greenBytes Inc. and LSI Corp. are also trying to make their marks on the green storage map, as have larger vendors like Dell Inc., EMC Corp. and NetApp. Most vendor initiatives so far involve adding energy-efficient enhancements rather than reengineering products.

"We're making some refinements to our product lines in light of the need for reduced power, cooling, space and the whole greening of the data center," said Larry Freeman, NetApp's senior marketing manager of storage efficiency. "Thin provisioning is key in power consumption." In addition to thin provisioning, NetApp software features like data deduplication and snapshots are designed to save capacity in VMware environments. In October 2008, the company said its multiprotocol arrays were 50% more space-efficient than other systems supporting VMware. NetApp even pledged to make up the difference for free to users who didn't see an improvement.

NetApp has also embraced solid-state drives (SSDs) with its Performance Acceleration Module (PAM), a solid-state secondary cache that Freeman said will eventually become a flash implementation. "We see the benefit of using secondary memory to enhance performance without adding more disk drives," he said.

Slow, slower and slowest

The idea of slowing down or stopping disk drives when they're not in use was popularized by Copan Systems with its Revolution line of disk-based backup systems that use massive array of idle disks (MAID) technology.

In Copan's arrays, disks are shut down completely when they're not needed; and because only a handful of disks may be active at one time, you can cram many more disks into a single array. Running all of the densely packed disks would suck power and generate excessive heat, but MAID significantly reduces power and cooling requirements.

Other vendors use similar approaches, but some don't shut down disks completely. By reducing power to disks or parking their read/write heads, power consumption is reduced, but the disks can spin up to operational speed relatively quickly when needed. For example, EMC Corp. offers policy-based drive spin-down in its Clariion CX4 arrays and Disk Library backup systems that puts inactive drives in sleep mode.

Nexsan Technologies Inc.'s AutoMAID, available with its SASBeast and SASBoy arrays, also uses policies to spin drives down in three stages -- each stage offers greater power savings but also requires more time for the drive to get up to speed again.

Copan, EMC and Nexsan are just a few examples of disk system vendors that slow or stop disks to save power; many array vendors offer similar capabilities.

Other vendors are also focusing on ways to save power. GreenBytes' Cypress NAS appliance for archiving long-term data aims to cut energy consumption up to 80%, while Enhance Technology's products feature virtualization and auto spin-down RAID controllers. And last May, EMC Corp. unveiled virtual tape libraries (VTLs) featuring data dedupe. Moreover, EMC's Clariion CX4 storage arrays, which Dell also sells, released with built-in spin-down capabilities.

As for Dell, most of its energy-efficient focus has been on utilization, tiering, spin down and solid-state drives.

"If you had some set of data that requires very high performance but not a lot of data, solid-state drives may be very economical in power consumption," said Eric Schott, director of product management at Dell. "It's also about floor space consumed and heat output, because for every dollar you're spending to power the equipment, you're spending a dollar to cool the equipment."

But the environmental benefits aren't the only things on vendors' minds when pushing energy-efficient products. Economic benefits are deemed equally as important.

"The messaging is around 'Go green to save carbon footprint,'" said Greg Schulz, founder and senior analyst at Stillwater, Minn.-based StorageIO Group and author of The Green and Virtual Data Center. "Most IT organizations don't have a carbon footprint issue. What they have are issues to sustain business growth, economic enhancement and productivity."

Seven ways to cut disk system power

As one of the few mechanical devices in the data center, disk arrays draw substantial power to keep disks spinning and make cooling systems work harder to dissipate the heat they throw off. Here are seven ways to cut a disk system's power requirements:

  1. Thin provisioning. Because thin provisioning ensures that applications only consume the capacity they truly need, you don't end up with a lot of spinning, nearly empty disks.
  2. Spin down. In arrays used for secondary applications or those that use disk intermittently, drives can be slowed down or stopped when not in use.
  3. Solid-state drives. Solid-state drives (SSDs) use a fraction of the power required by magnetic-media disks and produce far less heat, but the power savings may be offset by the cost of SSDs.
  4. Big disks. By using higher capacity disks (especially 1 TB, 1.5 TB or 2 TB drives) you can store more data using fewer disks.
  5. Small form factor disks. For apps that require more performance than what SATA delivers, 2.5-inch SAS drives use up to 50% less power than 3.5-inch high-performance drives.
  6. Data deduplication. Store less and you'll need fewer disks and thus save on power. Dedupe is one of the most effective ways to cut capacity.
  7. Virtualization. Like thin provisioning, storage virtualization helps you make better use of the storage you already have installed. So while you may not cut your power bill, you can keep it from rising.

On the management side, the notion of intelligent management -- like that of Adaptec -- is something Schulz said can be expected to continue.

"We've seen many vendors adding intelligent management as a second feature, just like a RAID level," Schulz said. "You're seeing vendors bring that to the table, but in a granular approach: Use it when needed."

Adaptec's software allows drives to be operated in three power states, including normal operation with full power and full RPMs; standby, with low power that spins at a lower RPM during idle times; and power-off.

Dell's Schott said intelligent management can bring forth several benefits that otherwise aren't there. "It's very important for a storage array to be energy efficient," he said. "But it's also helpful if the applications could also clue us in more. It's one thing if the storage arrays are doing it in the background, it's another if the application is telling you."

While some vendors aren't sure to what extent the demand for energy efficiency will impact their storage products, most are sure that products aimed at conserving power will continue to gain momentum.

"Some of this greenness is much more of a philosophy over the work that we do, rather than just a product feature or release feature," Schott said. "And you can always do better. Even when you reduce and improve a few things, you're not done."

BIO: Matt Perkins is an assistant editor for TechTarget's Enterprise Applications Media Group.

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