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Perpendicular Hard Drive Recording Technology

Vangie Beal
Last Updated May 24, 2021 8:01 am

In perpendicular recording, data bits are aligned vertically (not horizontally) – or perpendicular to the disk, allowing room for more data.

How can a 3.5-inch standard hard disk drive (HDD) possibly hold a terabyte of information? As manufacturers reached the limits of hard drive capacity, consumer demand for even higher capacity drives did not diminish. A relatively new recording technologycalled perpendicular recording, is being deployed to further increase hard drive storage capacities.

Recommended Reading:
For those unfamiliar with how hard drives work, we recommend you first read “Did You Know… What’s Inside a Hard Drive?

To understand how perpendicular recording has changed hard disk storage and increased storage capacities, you first need to understand conventional, longitudinal recording.

Longitudinal Recording

As indicated by the name, longitudinal recording is a method of recording data to a hard disk drive (HDD) in such a way that the data bits are aligned horizontally in relation to the drive’s spinning platter, which is parallel to the surface of the disk. Essentially, you are recording on a magnetic material, where bits (a collection of magnetized particles) are laid out end-to-end. Longitudinal recording is the actual method of how the bits are recorded on disk platters. The direction of this magnetic charge is horizontal to the media, meaning the north and south poles of the magnetized particles are lined parallel to the surface of the disk.

Longitudinal recording has been the standard method of recording for more than 50 years the first commercial hard drive was introduced in 1956. Over the years we have seen many technological changes to longitudinal recording, which have resulted in higher-capacity drives. We’ve moved from 5.25 inch drives to 2.5 inch drives, the number of platters and heads have been reduced all the while increasing areal density (which is the amount of data per square inch of media). With all of these changes however, the need to physically change the way data was written to the drive was also being considered to reach higher storage capacities.

Storage capacity with longitudinal recording was largely increased by decreasing the size of the magnetic grains that make-up data bits. As the magnetic grains became smaller, more data could then be stored on the disk. Unfortunately, magnetic grains have their limits. By continuing to shrink them, the point where data integrity would be compromised was on the horizon. This effect is called the superparamagnetic effect.

The Superparamagnetic Effect

In magnetic disk drive storage technology, the superparamagnetic effect refers to the fluctuation of magnetization due to thermal agitation. When the areal density (the number of bits that can be stored on a square inch of disk media) of a disk medium reaches 150 gigabits per square inch, the magnetic energy holding the bits in place on the medium becomes equal to the ambient thermal energy within the disk drive itself. When this happens, the bits are no longer held in a reliable state and can “flip,” and scramble the data that was previously recorded.

Because of superparamagnetism, hard drive technologies were expected to stop growing once they reached densities of 150 gigabits per square inch. Of course, when you see a hard drive manufacturer announce a 400GB hard drive you may wonder what happened to the superparamagnetic effect? Actually, this type of drive would contain three platters able to store up to a maximum of 133GB each resulting in a 400GB HDD, it is not 400GB contained on a single platter.

Perpendicular Recording

Realizing the limits of packing smaller magnetic grains was heading towards occurrences of superparamagnetism, manufacturers still needed a way to pack more data onto each drive. Perpendicular recording differs from longitudinal recording in that data bits are aligned vertically (not horizontally) or perpendicular to the disk, which allows for additional room on a disk to pack more data, thus, enabling higher recording densities. It is widely believed that with perpendicular recording, the superparamagnetism barrier can be pushed further back allowing for continued growth in the areal density of the media for some time.

Hitachi believes this recording technology, in time, can result in a 3.5-inch disk drive capable of storing an entire terabyte of data. Not only will perpendicular recording have an effect on desktop storage, but on consumer devices as well, which is a major driving force in storage sales. Smaller drives (1.8 inch), like those used in the popular Apple iPod will also grow in capacity . in due time we will see the iPod and similar devices offer 80GB of storage and higher. Alternatively, it could be used to produce much thinner and slimmer high capacity hard drives for consumer devices. Where you can store 3,000 on some of the higher-end MP3 players today; image being able to store 30,000 songs on one.

Perpendicular recording technology however will not start and stop with changing the way data bits are aligned. Much like the growth in capacity with longitudinal recording, technological advancements in platters; read/write heads, and physical disk media surfaces to name a couple, will contribute to advancements in the capacity growth of perpendicular hard disk drives.

Perpendicular recording technology also is not the answer to removing superparamagnetism. It has not stopped the search for the ever elusive answer to being able to further shrink the actual size of the magnetic grains that make up data bits. Perpendicular recording only moves the superparamagnetism barrier back a bit, it doesn’t eliminate it. For now Perpendicular recording technology allows for many new developments and advancements in storage capacity over the coming years, but it too will feel eventually feel the pull of the superparamagnetic effect; unless the physical size of a bit can be further reduced, then again that barrier will be pushed back to meet the ever-growing storage needs of consumers.

Did You Know…
According to iSuppli, the global hard disk drive (HDD) industry set an all-time record for growth in 2005, with shipments rising to 71 million units for the year.

Based in Nova Scotia, Vangie Beal is has been writing about technology for more than a decade. She is a frequent contributor to EcommerceGuide and managing editor at Webopedia. You can tweet her online @AuroraGG.

This article was originally published on April 21, 2006