Due in no small part to consumers’ demand for smaller, more reliable disk drives with larger capacities, the disk drive industry is shifting — in a perpendicular direction. With perpendicular recording, disk drives have a much higher capacity than the traditional longitudinal magnetic recording. And the technology appears to be coming of age.

For the past 50 years, disk drive makers have used longitudinal magnetic recording technology to store data. And for about the past decade, engineers and scientists have pondered the potential effects of a natural phenomenon called superparamagnetism; they have postulated when its presence might interfere with the progress of the hard disk drive (HDD) industry.

Well, it appears to be now.

One of the key challenges facing the hard drive industry is overcoming the constraints imposed by the superparamagnetic effect, which occurs when the microscopic magnetic grains on the disk become so tiny that they interfere with one another, thus losing their ability to hold their magnetic orientations. The result is “flipped bits” — bits whose magnetic north and south poles suddenly and spontaneously reverse — that corrupt data, rendering it and the storage device unreliable and thus unusable.

Because of this, and due in no small part to consumers’ demand for smaller, more reliable disk drives with larger capacities, the disk drive industry is changing — pushing the next-generation disk-drive technology in a perpendicular direction.

With perpendicular recording, disk drives have a much higher capacity than the traditional longitudinal magnetic recording.

Longitudinal magentic recording (LMR), as its name indicates, aligns the data bits horizontally, parallel to the surface of the disk. Over the years, however, longitudinal recording has reached its uppermost capacity, “which cannot exceed 100 gigabytes per platter because of thermal instability,” Electronic Business recently acknowledged (via EDN). Consequently, increasing the areal density (i.e., how much data can be packed into a given space) of a platter with LMR means shrinking data bits and packing them more tightly. If the data bits become too small, though, the magnetic energy holding them in place also decreases and thermal energy causes them to demagnetize. The previously recorded data is thus scrambled.

In contrast, perpendicular recording aligns the bits vertically, perpendicular to the disk, which allows additional room on a disk to pack more data, thus, enabling higher recording densities. Specifically, perpendicular recording is believed to be capable of delivering up to 10 times the storage density of longitudinal recording, on the same recording media. Bottom line: higher capacity in disk drives.

Although perpendicular recording has been in the research labs for more than two decades (There was some interest in using the system in floppy disks in the 1980s, but the system was never reliable.), today there is renewed interest in using it for hard drives, which are rapidly reaching their fundamental capacity limits.

In fact, many technical experts say it is the natural evolution of the disk drive industry. After all, it focuses on smaller and light form factors…and we consumers like our tech toys small in size but optimal in ability, be it our laptop computers, MP3 players or handheld digital video cameras. So it is of little surprise that these consumer electronics are driving the demand for smaller, more reliable disk drives with larger capacities.

HDDs using PMR appear to be coming of age as key vendors announce products or new breakthroughs featuring this technology.

Toshiba Storage Device Division has announced it would extend PMR technology to its “short” 1.8-inch HDD family. The new drives have a 10 percent smaller footprint than its first-generation 1.8-inch PMR HDDs and up to 80GB of capacity, the company said last month.

Hitachi Global Storage Technologies also announced last month that it has achieved an areal density achievement of 345 gigabits per square inch using PMR technology. This areal density, demonstrated in laboratory testing, represents an increase of more than two-and-a-half times the areal density of today’s highest-capacity products, the company said. Areal density is the number of bits of data that can be recorded onto the surface of a disk or platter, usually measured in square inches. In May, the company began shipping its first PMR drive, designed for notebook and mobile computers.

Other companies that have developed drives with perpendicular recording include Western Digital, Fujitsu Limited (a relative latecomer) and Seagate, the latter of which is considered the leader of PMR technology. In August, the company announced that it had shipped 700,000 units of the perpendicular 3.5-inch, 7,200-RPM drive, and of those, about 100,000 had a capacity of 750 gigabytes apiece. Seagate has disk drive product lines that use perpendicular recording in each of the major markets: desktop, notebook, enterprise and consumer electronics.

By the end of 2007, there will likely be about a dozen companies with PMR drives.

According to TrendFOCUS research and technical experts, areal density growth will average 40 percent compounded annually, allowing hard disk drive storage to maintain its capacity lead over flash (which Apple Computer uses in its iPod Nano) for the foreseeable future.

The three- to five-year target is 500-gigabit areal density and extensibility to more than one terabit — a tall order for any other than this stand-up technology.

Resources

Hard disk drive industry changes direction
by Debra Bulkeley
Electronic Business, Sept. 26, 2006

PMR drives come of age
Computer Technology Review, Sept. 19, 2006

Perpendicular Recording
Hitachi Global Storage Technologies

Going beyond perpendicular
by Chris Mellor
Tech World, Sept. 16, 2006

Perpendicular Recording: A Boon for Consumer Electronics
Hitachi Global Storage Technologies