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RAID changes its stripes, but not its value

RAID systems look a lot different today than they did two decades ago, but the concept remains the same: use multiple drives to protect data.

While industry experts say the shape of RAID storage systems have evolved and are handled differently than when they first appeared 20 years ago, the core concept of combining drives to protect data lives on regardless of the methods used.

"Is RAID still relevant? Absolutely. Is RAID still important? Absolutely. Is RAID losing its buzz, luster, sex appeal? Yeah," says Greg Schulz, founder and senior analyst at StorageIO Group, Stillwater, Minn. "What's taking its place? Distributed RAID, global RAID, hybrid RAID. We're seeing all of these new manifestations of RAID."

Experts say storage systems conceived during the last five years or so from Compellent Technologies Inc., EqualLogic Inc. (now part of Dell Inc.), LeftHand Networks Inc. (now part of Hewlett-Packard Co.), 3PAR and Pivot3 use alternatives to traditional RAID, such as distributed parity schemes and wide striping.

EMC Corp.'s Atmos and IBM Corp.'s XIV Storage System are new versions of storage systems that use distributed parity. Other systems that hit the market in 2008, such as Atrato Inc.'s Velocity 1000 (V1000) and Xiotech Corp.'s Emprise platform, use new technologies to avoid RAID rebuilds. There's disagreement in the industry over whether those systems are RAID or not, but Schulz says it doesn't matter to the people who use them.

"Most people understand RAID and relate to RAID," he says. "If they hear about a new scheme, they don't care if it's RAID. They say, 'Is it good? Is it reliable? Can I trust it? Is there overhead?'"

Stephen Foskett, director of data practice at Mountain View, Calif.-based storage consultant Contoural Inc., says RAID has been changing its stripes since EMC rolled out its venerable Symmetrix enterprise system in 1990.

"We don't use RAID anymore, we use something like RAID," says Foskett. "I call it post-RAID."

Foskett says instead of combining entire disks, today's systems combine a portion of each disk to reduce the impact of hot spots. "It's the same kind of technology -- parity, mirroring, striping -- and you're still putting them together similarly as we did with RAID," he says. "But instead of building a RAID set with disk and carving it up to use it, we're doing the reverse. We're deciding what we want to use, and protecting it with RAID."

The post-RAID that Foskett says began with Symmetrix has pushed traditional RAID from enterprise systems down to low-end storage.

"EMC would dispute this. They would say it [Symmetrix] is RAID," says Foskett. "But Symmetrix never did RAID. EMC deserves credit for it, even though they probably don't want it."

Andrew Reichman, senior analyst at Cambridge, Mass.-based Forrester Research Inc., says RAID is becoming more application-specific. For example, Oracle Automatic Storage Management (ASM) does its own software-based mirroring for data protection and requires no hardware RAID. "So hardware RAID may be de-emphasized for apps that have native data redundancy, but data redundancy of some kind will always be a part of the overall data protection arsenal," says Reichman.

One type of RAID that's increasing in value is RAID 6, which provides dual parity that makes it possible to recover from two disk failures simultaneously. That's a critical feature for organizations that use large capacity drives, particularly SATA.

Steve Prescott, director of technology at London-based post-production house Framestore, upgraded to Infortrend Technology Inc.'s EonStor RAID 6 controller to protect hundreds of terabytes stored in its render farm -- files that Framestore can't afford to lose.

"RAID is crucial to us," says Prescott. "We had been using RAID 5, but I thought if we could use RAID 6, let's do it. RAID 6 allows you to lose two drives. We wanted to make sure our system is as resilient as possible, and it's important that we don't lose any data during rendering."

Schulz says RAID is too embedded in storage technology to go away, but will continue to undergo fundamental change. "Look at all the activity around RAID 6, good, bad and indifferent," he says. "Will we see RAID 7 or RAID 8? I don't know. There's more noise around a distributed parity scheme.

"RAID is a commodity," adds Schulz. "The newer approaches tend to be more interesting. But that doesn't mean we're moving away from traditional RAID."

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