ATA makes inroads to network storage

Advanced Technology Attachment has long been the dominant hard drive technology in the PC world, where it is more commonly known as Integrated Drive Electronics. But ATA is breaking new ground in the enterprise arena, showing up in storage arrays used in direct-attached, storage-area network and network- attached storage settings.

The technology has gained the endorsement of such corporate storage players as EMC Corp., Network Appliance Inc. and Storage Technology Corp. A dramatic price/performance boost relative to other storage technologies has powered this unexpected upward migration, according to industry executives.

Mass-produced for PCs, ATA has always been cheaper than the SCSI and Fibre Channel disks that have dominated enterprise storage. But the price gap has grown so that ATA products now sell for a fraction of the cost of SCSI and Fibre Channel drives, industry analysts say. Meanwhile, ATA's performance and reliability have reached levels acceptable for certain storage applications, and the emergence of Serial ATA provides some of the industrial-strength characteristics of high-end disk technology.

The knock on ATA was that it wasn't fast or reliable, said Roger Cox, chief analyst for server storage and Redundant Array of Independent Disks (RAID) at Gartner Inc.'s Dataquest Inc. But "the specs for [Serial ATA] are better today than when Fibre Channel first came out in the late 1990s," he said.

ATA compares favorably to tape storage, which underperforms disk storage but is historically cheaper. ATA has found a home in applications for which SCSI and Fibre Channel are too expensive and tape is too slow.

In the federal sector, ATA has begun to carve a niche in nearline storage, also called midline, which represents a middle tier of storage in which data can temporarily reside as it moves from primary disk storage to tape. Data in nearline storage can be accessed more quickly than data that is immediately archived to tape.

Officials with the Air Force's 45th Space Wing are considering ATA as a way to do multilayer backups, said Glenn Exline, manager of information technology development at Patrick Air Force Base. When a restore is necessary, 90 percent of the data resides on the first three days of backups, he said. With the ATA approach, the base can restore data more quickly without purchasing expensive drives, he said.

Some vendors believe Serial ATA will be the technology used for nearline storage and other enterprise applications. "Serial ATA brings some feature sets missing from ATA that didn't make it prime time for the enterprise," said Barbara Murphy, vice president of marketing at 3ware Inc., a maker of parallel and serial RAID solutions. She cited such Serial ATA features as greater performance and hot-swappable drives, which enable users to change drives without taking the system off-line. ATA has a typical data transfer rate of 100 megabytes/sec, while Serial ATA has a 150 megabytes/sec rate. The technology's road map calls for 600 megabytes/sec bandwidth within a few years.

Products geared toward midline applications have hit the market. Maxtor Corp., for example, markets MaXLine drives, which are designed to be more durable than typical ATA devices. Midline products "need to run continuously to serve the data-center environment," said Robert Wise, director of product marketing at Maxtor. MaXLine products are available in both serial and parallel ATA forms.

Another federal application is fixed-content storage, used for archiving e-mail messages, image files and other data "that has to be online and available but is not necessarily being transacted" every day, Murphy said.

Similarly, Exline said his group is looking into ATA as a "potential candidate for seldom accessed data" for users who don't need the capabilities of a high-end storage array.

The need to back up surveillance video has also sparked government interest in ATA, which can provide cheap bulk storage for such capacity-hogging applications. In many cases, organizations have gone directly to ATA as an alternative to tape, said Craig Lyons, product marketing manager at Promise Technology Inc., an ATA RAID vendor.

With ATA, Wise said, customers "can get a lot more raw capacity and store more frames."

ATA Caveats

ATA has the potential to solve a number of government problems, but customers need to exercise judgment when deciding to deploy the technology. In high-transaction applications, for example, SCSI is still the better solution.

"SCSI technology lends itself to a higher-transaction environment," Murphy said. "You won't be running an Oracle [Corp.] database on ATA."

One reason is higher spindle speeds, which seek data faster. Top-of-the-line SCSI drives have spindle speeds of 15,000 rotations per minute, while many ATA drives operate at 7,200 RPM. Newer Serial ATA products, however, have hit the 10,000 RPM mark.

Performance is indeed an issue for some organizations.

"ATA could be a player, depending on the performance needs required," said Michelle Butler, technical program manager for the Storage-Enabling Technologies Group at the National Center for Supercomputing Applications. She said that ATA could find a role on some of NCSA's smaller infrastructure systems, such as the file servers that run Microsoft Corp.'s Windows NT. NCSA will purchase about 100 terabytes of disk storage this year.

Reliability is another factor, according to Alan Horwitz, director of advanced technology sales for Hewlett-Packard Co.'s federal operation. ATA is "still not as reliable as industrial-strength storage," he said. SCSI and Fibre Channel drives, he said, tend to have mean-time-before-failure (MTBF) ratings of more than 1 million hours, but ATA drives may only deliver 500,000 hours.

Sam Sirisena, vice president of sales and marketing worldwide at Promise Technology, however, believes the reliability gap is closing. He contends that recent ATA products have an MTBF rating of 1 million hours, up from 300,000 hours a few years ago and compared with 1.5 million hours for SCSI.

"In speaking to IT professionals who have either evaluated or implemented ATA-based arrays to complement their existing SCSI or [Fibre Channel] systems, the reliability of those ATA-based systems has not been called into question," said Pete Gerr, senior research analyst at Enterprise Storage Group Inc. "All indicators are that ATA-based systems provide a high level of reliability."

This coexistence may become a deployment trend. "Customers can have both Fibre Channel disks and ATA disks within the same array and managed with the same software," said Eric Endebrock, storage-area network product manager for Dell, which resells EMC solutions. ATA became an option for Dell/EMC Fibre Channel arrays earlier this year. "You can have very high-performance Fibre [Channel] disks and less expensive ATA disks for different purposes."

Moore is a freelance writer based in Syracuse, N.Y.

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How it works

Advanced Technology Attachment describes a class of high-capacity, low-cost drives developed for the PC market but increasingly found in storage arrays and entry-level servers. ATA drives have a data transfer rate of 100 megabytes/ sec (except for high-end ATA/133, which performs at 133 megabytes/sec) and operate at up to 7,200 rotations per minute.

The newer-generation Serial ATA drives have a data rate of 150 megabytes/sec. Individual Serial ATA products spin as fast as 10,000 RPM. ATA and Serial ATA drive capacities vary widely but generally top out around 300G. In contrast, SCSI disks start at 10,000 RPM and run as fast as 15,000 RPM. Top-end Ultra320 SCSI products have a data rate of 320 megabytes/sec.

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By the numbers

Organizations selecting ATA drives may well reap immediate financial benefits. A June study by Enterprise Storage Group Inc. shows that ATA drives can be had for one-sixth the cost of SCSI drives. The gap is somewhat narrower for high-end Serial ATA drives, which average about one-third the cost of SCSI drives. The report pegs the average cost of ATA drives at $1.21 per gigabyte, Serial ATA at $2.38 per gigabyte and SCSI at $7.99 per gigabyte. Fibre Channel disks, meanwhile, are 10 times the cost of ATA and 5 times the cost of Serial ATA drives.