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A growing number of vendors now offer ATA-based RAID products. Many of these firms focus on the small business and low-end server markets with RAID products supporting a small number of direct-attached ATA drives. Others have focused on "RAID on a chip" ASIC solutions designed to move disk array support onto the system motherboard.
But a handful of companies - including 3ware, Consensys, and ExaDrive - have set their sights on the enterprise RAID market. These firms have developed ATA-based direct- or network-attached RAID products designed to match or even exceed the performance of SCSI- or Fibre-based arrays. Consensys' Raidzone product line, for example, uses a proprietary backplane and controllers that the company claims will equal or exceed the data throughput of systems using Ultra SCSI bus. "We don't give up anything to the SCSI and Fibre Channel arrays except the price," Ripley says. Other ATA-based RAID products, such as ExaDrive Networks' Diamond series, use a hybrid approach: They combine ATA disks with multiple SCSI or FC host interfaces and a proprietary controller.
According to the manufacturers, these ATA-based RAID products offer many of the same benefits as SCSI-based arrays. They typically support all standard RAID levels, including RAID 5, and they include hot-swap and hot-spare capabilities with automated failure detection, failover and data remirroring. They also provide policy-based management
ExaDrive Networks' Klein also noted that ExaDrive certifies the interoperability of its arrays with a variety of third-party products, including FC switches, storage virtualization, SAN management tools, and operating systems. "We approach the market differently than the big turnkey vendors. We say if you're looking for a best-of-breed approach, that's where we come in," he says. "The hardware savings give customers a margin to figure out where to get the best software solutions from high-end VARs and integrators. That's why we put a big emphasis on interoperability, especially on the Fibre Channel side for [storage area network] SAN implementations."
|Serial ATA and iSCSI|
ATA finds its niche - and more
So far, ATA-based RAID has received the warmest welcome in certain vertical markets. "Our major users include government and university research laboratories, oil and gas exploration, video surveillance, data storage and other customers who produce very large amounts of data," says Consensys' Ripley. "In many cases, there's no other affordable way to store that data without using tape or optical storage, and that means giving up immediate access to the data."
According to Scott Studham, group leader in the Pacific Northwest National Laboratory's molecular science computing facility in Richland, WA, the cost-performance relationship between ATA and SCSI was a decisive issue in the group's decision to invest heavily in ATA-based disk arrays. Studham says the laboratory recently migrated its supercomputer data archives from a 20TB tape-based system to an ATA-based storage array. In addition, he says the laboratory will use a 200TB ATA-based RAID array as primary storage for its new supercomputer, which he says will be the world's largest and fastest Linux-based system.
"A lot of people asked why we weren't using SCSI [RAID technology], but once I presented the facts, they all understood," Studham says, referring to the conclusions he reached about the performance and reliability of ATA-based disks vs. more expensive SCSI hardware. "In this environment, that 4% to 5% performance penalty for using ATA instead of SCSI doesn't outweigh the 200% to 300% price difference."
In the mainstream enterprise market, ATA-based RAID has also emerged as an alternative to tape-based backup systems and to nearline systems such as CD jukeboxes. As disk prices fall and ATA-based RAID products become more sophisticated, these products have created a new and rapidly-growing niche in the nearline storage market.
According to Jamie Riis, CIO of BayView Financial, a mortgage bank based in Miami, FL, moving to ATA-based nearline storage yielded significant benefits. BayView currently uses a Network Appliance NearStore R100 system to store backup data snapshots before moving them over to tape-based storage, allowing the company to provide almost instant access to recent backups. "It could take up to 20 hours to get this data from the tape system," Riis says. "Now if someone loses a file, we can go back at least to where they were at the last snapshot and restore the data in a few minutes."
In addition, Riis says BayView also plans to migrate its document image archives from an optical jukebox to the R100. "We'll go from a system where it takes 30 to 40 seconds to retrieve an image and we have to throttle user access, to an environment where hundreds of users are getting submillisecond access," he says.
According to Chris Bennett, director of product marketing for Network Appliance, Sunnyvale, CA, Riis' comments reflect an important trend for ATA-based enterprise storage: "ATA drive technology is enabling the industry to store information online that previously was not available," he says. "When you're comparing the amount of data now stored online to the amount stored on tapes stacked in cardboard boxes someplace, you're talking about orders of magnitude of difference."
Major vendors respond
Some top-tier vendors - such as IBM, Network Appliance, and EMC - have released ATA-based RAID products designed for nearline storage, disk-to-disk backup systems, or even as mainline storage for mid-market enterprise customers (see "Major vendors introduce ATA RAID products.")
Unlike their smaller competitors, these firms are more conservative about the short-term prospects for ATA-based RAID. "We don't yet see customers who are willing to put mission-critical data on ATA drives," Vaughn says. "You still get better performance with SCSI technology, and that performance advantage is clear. The ATA platform is important, but we're using it to target the midmarket and distributed environments right now."
Nevertheless, according to Bennett, Network Appliance was surprised by the response to its ATA-based NearStore product line, which began shipping in January 2002. "We've shifted significant resources onto NearStore because of the exceptional response," he says. "But we also want to position it where it's appropriate. It's not just a performance issue, it's an availability issue - the [ATA] drives are slower and more prone to failure, and you run a higher risk of degrading critical operations in an ATA environment."
This was first published in October 2002