Energy-saving architecture puts a new spin on disk storage.
Organizations that are struggling with cost and power-consumption issues in the data center have begun to take a long, hard look at their storage infrastructures. While it is generally agreed that dense servers are the No. 1 culprit in the current power and cooling challenges, networked storage is not far behind.
It is estimated that increases in average storage rack density will drive average power consumption from 2kW per rack to 30kW per rack over the next 12 months — and that’s only half the story. For each watt used by the server or storage, A/C, power supplies and other related equipment together require nearly 1.5 times that amount.
“Power consumption levels in the data center are at an unprecedented high, and will only increase,” said Roger Archibald, senior vice president of marketing and business development for storage vendor Copan. “Soon, data center managers will be seeing up to 40 percent of their total budget attributed just to energy. Storage alone already consumes more than 30 percent of the total energy in a typical enterprise data center. The explosion of persistent data, or data that is retained for long periods of time, compounds this problem, as customers continue to add more and more capacity to manage it.”
Spin Doctor
A relatively new storage architecture known as Massive Array of Idle Disks (MAID) is gaining increased visibility due to its potential for dramatically reducing power, space and cooling costs. Industry experts say MAID technology can help customers realize 75 percent or more in energy savings compared to typical RAID (redundant array of independent disks) systems.
MAID systems are built with densely packed arrays of low-cost Serial ATA (SATA) disks. But unlike SATA arrays that feature hundreds of spinning disks, a MAID system has the ability to turn disks on and off as necessary — a feature that conserves power, reduces heat, allows greater storage density and extends the useful life of the disks themselves.
The MAID approach essentially treats the disk drives as tapes in a library. A MAID array contains hundreds of terabytes of disk in a single cabinet, in which the disks share cabling, power and a controller.
The MAID approach, which was developed by computer scientists at the University of Colorado in 2002, relies on algorithms to monitor and minimize activity of drives in the array. Typically, only about 25 percent of the disks in a MAID array — the ones that contain the data most likely to be used — are actually moving at any one time.
Inactive disks are powered down and then spun up again when needed. Reactivation typically takes less than 10 seconds. Disks are spun on a regular basis even when not used to keep them operational. This so-called duty cycle management can reduce the number of stops experienced by a drive by 25 percent. For comparison, a typical ATA drive is built for 40,000 stops over its life.
MAID technology has been championed by Copan, Fujitsu and Nexsan, but EMC announced in October that it will also enter the MAID market in early 2008. Hitachi Data Systems offers a similar disk-based, power-saving technology but with a different approach. Rather than idle disks that spin up when needed, HDS’s Power Savings Storage Service (PSSS) features constantly spinning disks that can be powered down when they aren’t needed.
Cutting the Tape
Beyond the decreased space, power and cooling requirements, MAID offers an ideal platform for long-term, online storage of persistent data. Large-scale disk storage systems based on MAID architecture allow dense packaging of drives and sufficiently high throughput for data that is accessed infrequently.
This type of data traditionally has been stored on write once, read many (WORM) tape, rather than the more expensive spinning disks of RAID arrays. Tape has always made a lot of sense due to its superior scalability and affordability — tape costs three to five times less than even the lowest-priced disk technology.
But the fast-retrieval requirements included in many of the recent federal regulations are forcing a rethinking of that strategy. MAID offers the accelerated access and retrieval capabilities of disk with a total cost of ownership that is competitive with tape. According to a Forrester Research report, a MAID gives organizations the ability to keep a copy of deep archive data onsite in a readily processable format that can save months of staff time and millions of dollars.
Taneja Group technology analysts say MAID technology will play a key role in reshaping overall user attitudes towards both tape and standard disk deployments for secondary storage tiers.
“The emergence of MAID is a very critical development in the storage tiering landscape, and there are strong implications for the vast majority of enterprise IT shops,” Taneja analysts wrote. “Because of its potential long-term impact, we believe MAID warrants serious consideration by any team evaluating tiered storage today.”
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