Navigating the new drives

What's the best drive for your shop? That depends on your specific needs. Vendors are cranking out cheaper drives for increasingly specialized applications.

Platter capacities plateau

Per-platter capacities for 3.5-inch disk drives hit the wall in 2003. Vendors expect to post incremental density gains going forward, until new technologies can reach the market.

Keeping track of disk technology used to be easy: Each year, you could count on capacities to go up, performance to improve and drives to become more reliable. But those metrics don't apply to what's happening today.

Manufacturers such as Hitachi Global Storage Technologies (HGST), Maxtor Corp., Seagate Technology and Western Digital Corp. no longer focus on doubling capacities or spinning platters at faster and faster rates. Instead, emerging products are being tailored to increasingly specific missions, from affordable ATA drives for nearline storage to compact form-factor designs for blade server environments. New lower-cost drives are ushering in new ways to do backups.

Storage managers should see an explosion of disk storage options, punctuated by four key trends in the next 12 to 18 months:

  1. Leveling off of capacity growth
  2. New serial-based drive interfaces
  3. Smaller form factor drives
  4. Increasing drive category crossover
The flattening capacity curve
In 2002, drive capacities hit the brakes. Capacity figures that once doubled every year are now expected to double only once every two or three years. (For another perspective on disk drives, see "Best Practices: Five axioms for storage") The culprit is the increasingly difficult challenges in boosting areal density. Currently, the largest ATA drives weigh in at 400GB--a figure that won't likely double before the end of 2006. In fact, the bump from 300GB to 400GB drives earlier this year was achieved not by increasing areal density, but by adding a fifth platter to the drive packaging.

Sharply higher capacities are emerging in SCSI and Fibre Channel drives, which traditionally have lagged well behind their ATA counterparts. New products such as Hitachi Global Storage Technologies' Ultrastar 10K300 and Fujitsu's MAT3300NC/NP offer peak capacities of 300GB--up from 146GB last year. Seagate is also expected to roll out high-capacity Fibre Channel disk drives. Initial product is expected to hit the streets in volume this summer and fall.

None of the vendors expects sales of so-called "fat fibre" drives to account for more than a small fraction of SCSI and Fibre Channel disk sales. One reason: Enormous drives can take several hours or even days to rebuild following a disk failure. That leaves a typical RAID array wide open to catastrophic data loss during the rebuild process. Network Appliance Inc. (NetApp) delivered a product earlier this year with its dual-parity (DP) architecture, which puts two dedicated parity drives behind the primary disk. But a DP-like product imposes costs that once again slant the argument in favor of less-spacious drives.

Massive drives can also limit the performance of storage arrays, which rely on parallel disk access to speed reads and writes. The new class of drives should find a ready home in direct-attached server storage, and may offer a good fit for Fibre Channel-aligned enterprises supporting less-critical backup and archive applications. For enterprise storage arrays, however, the capacity sweet spot will not likely shift out of the 73GB range, despite the arrival of jumbo 300GB Fibre Channel drives.

Recommendation: For non-critical, RAID-enabled environments, consider 300GB ATA drives--they offer excellent costs per gigabyte and acceptable reliability.

Serial switch over
Drive makers are replacing a pair of venerable storage interfaces--ATA and SCSI--with new serial-based offerings. Serial ATA (SATA) and Serial-Attached SCSI (SAS) offer extended features, improved management and a fresh performance roadmap. It's a transition with far-reaching implications because everything from disk arrays to server backplanes must adapt to the new interfaces.

SATA drives and compatible systems have been shipping for more than six months and are rapidly displacing parallel ATA solutions. Some SATA-savvy array products include EMC Corp.'s Clariion and Network Appliance Inc.'s NearStore R200. LSI Logic Corp. also produces a pair of SATA-capable arrays for its OEM customers. With 1.5Gb/s data rates, SATA boasts a well-formed roadmap that includes provisions for command queuing and reordering, multiple ports and a one-meter cable for enhanced design flexibility. SATA is also being built into new array offerings, which could push established vendors to roll out SATA-enabled midrange arrays of their own.

Steve Kenniston, technology analyst for the Enterprise Storage Group (ESG), says demand for affordable, high-capacity disk storage is driving SATA. A recent survey by ESG indicates that nearly 25% of respondents currently use disks in their backup environment. "That's climbing to 80% in the next two years," says Kenniston.

Future versions of SATA will boost data rates to 3Gb/s, while remaining backward compatible with 1.5Gb/s SATA gear. A 6Gb/s SATA spec is on the roadmap, though drives based on this technology are years away.

The recently approved SAS standard will take longer to arrive. Prototype products--from Maxtor, Seagate and others--have appeared at trade shows, and the SCSI Technical Association (STA) has been conducting plug-fests to ensure interoperability. The new standard offers 4Gb/s data rates out of the box, while the SAS roadmap calls for transfer rates as high as 12Gb/s.

Like SATA, SAS improves flexibility, providing support for hardware that can theoretically support more than 16,000 drives. In an interesting twist, the SAS interface is actually a superset of the SATA pinout, which means a SAS backplane can support both SAS and SATA drives. And like SATA, the SAS interconnect employs more compact cabling and connectors, which simplifies management and streamlines server and chassis designs. The first SAS products should hit the market at the end of 2004 or early 2005.

"You still have a pretty significant legacy volume of Ultra 320 SCSI through 2005," says Joel Hagberg, vice president of marketing at Fujitsu. "As you go into '06, most manufacturers are into the end-of-life planning for U320 SCSI."

Stephanie Balaouras, senior analyst in the enterprise computing and networking practice at the Yankee Group, expects SAS products to be limited to direct-attached storage (DAS). She cites the falling cost of Fibre Channel drives and the increasing reliability and utility of SATA drives, creating a squeeze in the middle for late-arriving SAS products.

Kenniston is more direct: "I only know of one company pushing Serial-Attached SCSI, and that's HP. It's on all the vendor roadmaps to have something, but I don't see SAS being their number one priority," Kenniston says.

International Data Corp. expects SAS hard drive production to reach 8.1 million units by 2007. By comparison, some 8.8 million parallel SCSI drives and 8.5 million Fibre Channel drives are expected to ship in the same timeframe. One thing that will delay volume sales of SAS drives is the transition of server backplanes from parallel SCSI to the serial variant.

Recommendation: IT shops should deploy servers that provide native support for SATA and/or SAS as they become available, in order to prepare for future drive deployments. Start planning to incorporate SATA arrays into your storage environment for nearline disk storage.

Next-generation technologies
to boost platter density
Current giant magneto-resistive (GMR) head technology and longitudinal recording techniques are approaching physical limits. Bits are packed so tightly on the platter that the magnetic charge used to denote a one or zero can flip spontaneously if things are compacted much more.

Vendors are turning to some new technologies to overcome this hurdle. One approach--demonstrated late last year by Maxtor Corp.--embeds magnetic elements vertically into the disk surface, allowing bits to be more tightly packed on the platter. Known as perpendicular recording, Maxtor's demonstration of the technology produced a per platter density of 175GB, nearly double that of any product currently on the market.

Another approach, called heat-assisted recording, takes a page from optical drive technology. This process employs media that will only switch magnetic orientation when heated to a specific temperature. The approach eliminates the danger of spontaneous field change, but at a cost in complexity because a laser must heat the media. While promising, both techniques require significant investment and a changeover in drive manufacturing and supply. In short, it will be years before either approach will drive up disk densities.

Form over function
Even as drive makers jigger the interface, they are hard at work shrinking the drive enclosures. Seagate recently launched its Savvio line of small form factor enterprise-class drives based on a 2.5-inch package. The size reduction from current 3.5-inch designs offers a host of benefits, including a smaller footprint, lower power consumption and heat output and reduced acoustic and vibration levels. Later this year, expect to see 10K rpms 2.5-inch drives. The wait for 15K rpms high-performance 2.5-inch drives will extend at least into 2006 and possibly later.

Brian Kraus, senior global marketing manager at Seagate, says the smaller drives allow 1U servers to hold a complete, four-disk RAID 5 array, with redundant disks dedicated to data and to the operating system. By contrast, 3.5-inch drives require a 3U server design to provide the same capability.

Both Maxtor and Seagate have announced 2.5-inch form factor drives, with production models expected to reach the market in the second half of 2004. Initial designs will be relegated to DAS, while array makers such as EMC and HDS mull the significant costs of reengineering cabinets and plumbing for the new drives.

Joe DeRosa, senior director of enterprise storage marketing for Maxtor, expects that small form factor drives will make headway in the market in 2005, with measurable volumes occurring in 2006. Once the small form factor tide turns, the switchover should happen fast. Gartner Inc. projects that that by 2007, 2.5-inch form factor drives will lead enterprise sales.

The smaller drives could enable new breeds of disk-based storage. ESG's Kenniston sees a future where companies can buy sealed 2U boxes with multiple terabytes of storage, which can be plugged into a SATA or other connections. The result is truly commoditized disk storage that can serve anything short of critical applications.

For example, SpectraLogic sells a 12-disk cartridge that plugs directly into the company's Spectra T950 tape library. A Spectra RXT cartridge can hold up to 1TB of RAID-protected data, for fast, virtual tape library functionality. It's an approach that could gain momentum as enterprise-ready, 2.5-inch form factor drives hit the market at reasonable price points.

Recommendation: Small form factor drives are an exciting development, but the early premium charged for these products will hinder proliferation. Until prices for 2.5-inch models drop--probably in 2006--most shops will find themselves well served by the traditional 3.5-inch form factor offerings.

Category crossovers
The increased number of drive technologies targeting the middle of the enterprise drive market reflects a significant crossover of product categories that began in 2003. The arrival of the first so-called "Enterprise ATA" drives from Maxtor and Western Digital has kicked off a mingling of drive types, and the trend shows no signs of abating through the end of 2005.

The second-half of 2004 should see significant sales of enterprise ATA drives, with large volumes going into nearline and emulated tape storage solutions. These ATA drives typically offer mean time between failure (MTBF) numbers close to one million hours--significantly higher than desktop-rated ATA drives.

Driving the trend are continuing improvements in reliability from ATA-based products--improvements that could shake up vendor product lines, says ESG's Kenniston. "Over the next 12 to 18 months, the quality of ATA will get significantly better and it will be driving increased sales," says Kenniston, adding that "vendors are often more scared about positioning--why is the 2.5 times the cost for Fibre Channel worth it?"

It's a good question, and one that Hewlett-Packard Co. recently sought to answer when it announced a new class of Fibre Channel-based drives called Fibre-Attached Technology Adapted (FATA). FATA drives offer native Fibre Channel protocol operation--enabling enterprise customers to standardize on a single storage architecture, while delivering significantly reduced costs. Yankee Group's Balaouras expects that FATA-based drives could be priced about 30% below those of similar capacity Fibre Channel drives and will offer capacity up to 250GB with a dual-port, 2GB/s, Fibre Channel interface.

Recommendation: If you're standardized on Fibre Channel now, FATA can help keep the environment simple while offering good reliability and performance. Mixed environments can benefit from the improving reliability of enterprise ATA drives.

This was first published in June 2004
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