NEW YORK After successfully postponing a crucial technology transition for decades through process re-engineering, the hard-disk drive (HDD) industry is finally coming to terms with the reality that many of its underlying technologies are approaching their performance limits.
Starting this year and accelerating in 2004, HDD manufacturers and component suppliers are gearing up to debut faster, more cost-effective, less power-hungry serial technologies to replace parallel SCSI and ATA (Advanced Technology Attachment) interfaces for desktop and enterprise computing.
But while Serial Attached SCSI (SAS) and Serial ATA (SATA) will give the current generation of IT equipment a major performance boost, the most fundamental change in the history of the HDD market is actually taking place in a different arena. Industry executives say the longitudinal recording technology that has formed the bedrock of the HDD market soon will be replaced by perpendicular recording processes.
"We are running up close to the limits of the fundamental physics of longitudinal technology," said Ian Vogelesang, vice president of marketing at Hitachi Global Storage Technologies (HGST), the disk drive joint venture between Hitachi Ltd. and IBM Corp.
"The HDD industry had been increasing recording density at a rate of 100% per year, but because of the increasing difficulty in longitudinal recording, we now have an outlook of more like 60% ," said Gary Gentry, vice president of marketing and planning at Seagate Technology HDD Holdings, Scotts Valley, Calif.
"The industry at large has been working on perpendicular recording for at least 20 years and it is a difficult technology, but we believe that finally it is coming together." Gentry said.
Most industry executives said the advent of perpendicular recording is still two to five years away. Although working prototypes have been developed, they were at less than desirable recording densities.
"Perpendicular recording holds promise for the future," said Chuck Nielson, chief technologist at Fujitsu America Ltd. "The difficulty is that it is an entirely different phenomenon. It requires a whole new approach to head and media designs. This adds to the uncertainty of when it can happen."
Instead of rushing the deployment of perpendicular recording, Fujitsu has initiated plans to advance longitudinal recording, "giving us more time to continue this discovery phase," Nielson said.
Meanwhile, HGST and rival Seagate, while conceding that the technology has not reached prime time, are working hard behind the scenes to introduce it within a few years.
As opposed to longitudinal recording, where the bits are impressed in a parallel format along the surface of a disc, perpendicular recording stands the bits on end, enabling more data storage per square inch.
Perpendicular recording will be required at the point when products reach capacities of about 100- to 200Gbits per sq. in., compared to approximately 50Gbits today, industry observers said.
"Once we master perpendicular recording, it will be the foundation for the industry up to the point of approaching 1Tbit per sq. in.," said Seagate's Gentry. What's holding back the deployment? Reliability.
In an industry where differentiation is based on manufacturing execution rather than technology, product reliability is not something any supplier is willing to compromise. And, although HDD suppliers, including HGST, Seagate, and Read-Rite Corp., Fremont, Calif., have demonstrated drives based on perpendicular recording, kinks remain.
"Perpendicular recording still has issues," Gentry said. "The No. 1 thing for our customers is reliability and the No. 2 is cost. You have to have all these things there at a very mature stage before a customer can take that to market."
In the interface area, there are hardly any doubts as to the readiness of serial technology. In fact, disk drive manufacturers and component suppliers, including Agere Systems, Intel and LSI Logic. have collaborated to develop the specifications for the most extensive interface transition in the history of the storage industry.
"In general, from our customers we are hearing a strong desire to transition to serial interfaces," said Joe Borak, director of marketing for the storage division at Agere in Allentown, Pa. "This is for all three serial interfaces -- Serial ATA, Serial Attached SCSI, and Fibre Channel."
Borak said Agere has worked closely with HDD suppliers like Maxtor Corp. to develop integrated chips that incorporate the serial ATA physical interface, eliminating the need for a bridge chip. The early joint-development efforts with companies like Agere and LSI Logic enabled Maxtor in June to begin shipping 80- and 120Gbyte SATA devices to retailers.
Both ATA and SCSI have limits that SATA and SAS are expected to correct. For instance, ATA has a 5V tolerance, leading to electrical issues. Serial interfaces are based on point-to-point connections instead of shared media and offer higher transmission speeds.
"We always have concerns about new connectors and backplane designs but those problems are minimized in a serial environment where the wiring is point-to-point," Fujitsu's Nielson said. "In a Parallel SCSI bus, you would have the same set of wires going from the host bus adapter to each and every hard disk drive and so the signal integrity is an issue."
This is especially important in the enterprise market where SAS is seen improving performance dramatically, although the full introduction of the interface is about a year away.
"In a Parallel SCSI environment, you can have one controller and up to 15 devices on a cable, so they are all sharing a total bandwidth of 320Mbytes/s," Nielson said. "That turns into an average of just over 20Mbytes/s.
"In Serial SCSI, the interface speed is 300Mbytes/s but that is dedicated to a single device," he added. "So each device has available to it 300Mbytes/s of interface bandwidth and that creates the opportunity for much higher-performance systems."
The development of SATA, which is used mainly in the PC market, began well before SAS and as a result its deployment is already in full swing. Apple Computer Inc.'s new G5 computers are all SATA-based while Intel systems will by the end of this year be based on the new interface. The industry collaboration in the development of SATA specifications has helped in the smooth rollout of the technology, according to industry executives.
SAS is benefitting from some of the preliminary work done by the SATA working group, hastening its adoption and rollout in the enterprise market where other technology changes are afoot. HDD manufacturers said they expect to start replacing 3.5in. disk drives with smaller 2.5in. devices in enterprise products sometime within the next year.
"End customers are looking for ways to improve performance density and you need to go to smaller drives to improve the total cost of ownership," said Seagate's Gentry.
That form factor change could help accelerate performance in the sector, according to Seagate, which plans to introduce its first 2.5in. drives in 2004.