In-Depth

RAID and the Road to Greener Storage

Ratcheting back on disk power costs via RAID controller management software is one approach to "going green."

• By Jon William Toigo
• 09/09/2008

The latest announcements on storage "greening" are coming from RAID controller maker Adaptec Corporation. Last week, the company introduced Adaptec Intelligent Power Management, a new capability that "allows system OEMs, integrators and IT managers to easily custom-configure storage systems to reduce power consumption by up to 70 percent without sacrificing performance," according to the company.

Intelligent Power Management is now integrated into all of Adaptec's high-performance Series 5 and Series 2 Unified Serial RAID controllers, and enables SATA and SAS drives to be operated in three power states described as "normal operation" (full power, full RPM), "standby1" (a low-power mode that spins disks at lower RPM during idle periods), and "power-off" (disks not spinning). Additionally, the technology enables administrators to specify "blackout periods" during which power management features are disabled.

According to Suresh Pannikar, director of marketing at Adaptec, the green RAID technology is positioned to support disk-to-disk backup, archive, and file and print servers. "These applications do not require drives to be spinning at full power all of the time," he said in a pre-briefing on the announcement. Pannikar also cited numbers from the trade press and from analyst firm IDC showing that disk drives comprise about 33 percent of power consumption in finished storage arrays, totaling over $1.3 billion in annual energy costs in data centers worldwide.

Ratcheting back on disk power costs via RAID controller management software is an interesting approach. Disk drive manufacturers are enabling disk devices with low power modes, typically via electronics pack firmware enhancements and through the augmentation of spinning rust with flash memory caching. Adaptec supports 122 drives that sport spin-down modes.

At a system level, companies such as COPAN Systems have been leveraging drive spin-down capabilities for several years to reduce the energy consumption of massive arrays of independent disks (MAID) used as secondary storage. COPAN was first to get the nod as a "green-er" storage technology from Pacific Gas and Electric, as previously reported here. The question is whether drive idling at an intelligent RAID controller level might not enable COPAN-like functionality to become commonplace in even the most generic and low-priced "white box" arrays. If products such as Adaptec's Intelligent Power Management-enabled RAID cards make their way into more systems, what will happen to COPAN's most prized product discriminator?

Scott Cleland, director of world wide marketing for AMCC (which owns Adaptec competitor 3WARE), acknowledges the importance of doing whatever is possible to limit power, but notes that other issues are just as important to his customers. AMCC sells primarily to distributors, while Adaptec sells broadly to VARs and system integrators. According to Cleland, support for 6 Gb/s, the next step in the SAS interface and for PCIx Generation 2, is critical. AMCC will leverage its own PowerPC chip technology to enable this step.

RAID support is also important, he said. "RAID 5 is still predominant, but many companies are going to RAID 6 to shorten rebuild times on higher capacity drives that are entering the market." AMCC offers RAID 6 today as an option on its latest adapters, but at the end of this month, Cleland reported, a firmware patch will enable its SAS controllers "to do intelligent, scaleable I/O and to expedite drive rebuilds using traditional RAID 5."

"RAID 6 introduces a write penalty that is about five percent greater than RAID 5. Our firmware release will deliver a revolutionary performance upgrade in host-based RAID systems," he said.

Also important to market success for the RAID makers, according to Cleland, is energy efficiency of the card itself. In the effort to green the controller, there is no clear leader, Cleland argues. Every RAID card manufacturer confronts the same requirement to make all of the chips on a RAID adapter operate within the same 25 watt maximum limit. His 24-port adapter currently does the job at 17 watts, but to get really green, he said, "we need to go from 90 nanometer chip technology to 45 nanometers." In the meantime, he noted, "we have a group that is dedicated to looking at ways to throttle back our processor when performance is not needed."

As for greening drive operations, "AMCC offers APIs to enable software developers to decide when to spin down drives." It is less elegant, perhaps, than the graphical user interface provided by Adaptec, but may, in the end, accomplish the same goal: an overall reduction in the power consumed by spinning rust.

In the realm of green IT operations, there is a generally agreed-upon idea in the market that every little bit helps. Improving the energy efficiency of power supplies and chip sets is every bit as important as building in simple-to-implement energy-saver modes in drives. Some vendors, such as COPAN Systems, are seeking to drive this model to the platform level. They have recently announced a capability, in conjunction with Quantum, that will index and migrate data to a non-power-optimized disk array, then to COPAN MAID, and then to tape, creating a hierarchical storage-management scheme for distributed storage. Such a scheme, although not very granular from a data management perspective (data is moved based on date last modified/accessed and not on the basis of any intrinsic business value), can help defer the requirement to add more spindles to host an ever expanding complement of data.

The real greening of data storage, however, ultimately requires the grooming of data itself. That involves a combination of data hygiene (to eliminate duplicates and dreck) and classification as well as intelligent archiving. In turn, such an approach requires a more business process-focused and less storage platform-focused approach than is being advanced by drive manufacturers, RAID developers, or storage platform providers.

In a future column I'll interview QStar's director of marketing and business development, Jim Wheeler, and his company's ongoing efforts to help companies achieve greater power efficiency using archive technology for less frequently accessed data, whether to spin down disk, tape, or optical media. Until then, your comments are welcome: jtoigo@toigopartners.com.