What are Perpendicular Drives?

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  • Written By: R. Kayne
  • Edited By: Niki Foster
  • Last Modified Date: 08 November 2019
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Perpendicular drives are hard disk storage devices that store data bits vertically rather than “flat” or horizontally. Vertical storage allows for a ten-fold increase in data capacity while preserving data integrity.

Traditional hard disks store data bits horizontally on the surface of a platter. To increase drive capacity, bits have been reduced in size to fit more data. However, when bit density becomes too great, the magnetic particles begin to interfere with one another, causing bits to “flip” or reverse orientation. This is referred to as the super para-magnetic effect and results in corrupt or lost data.

To overcome this density barrier, perpendicular drives use slightly thicker platters designed to store “embedded” data bits vertically. A head floats over the platter, creating a magnetic field that orients the data bits to an “up” or “down” orientation.

For a rough comparison, imagine a bookshelf with a single layer of books laid flat, end-to-end across the shelf. This represents the way traditional platters hold data bits. Now stand the books vertically and press them to one side, and you can fit many more books on the same size shelf. This is the basic principle behind perpendicular drives.


Because perpendicular drives can hold so much more data per platter, they are well suited for mobile devices like laptops and portable audio players. As an example, Hitachi points out that a 6-gigabyte micro drive used in MP3 players holds about 3,000 songs. Using perpendicular technology, the drive could hold 30,000 songs. Industry insiders claim the price of drives will continue to fall despite the new technology. Perpendicular drives should be less per gigabyte than the same size standard drive, as material cost is reduced when more data fits on fewer platters.

Toshiba was the first manufacturer to market perpendicular drives in August 2005. Hitachi followed, while Seagate, Fujitsu and other manufacturers are also releasing perpendicular drives. Initial product is aimed at laptops and electronic devices, but general use perpendicular drives will soon follow. Hitachi reportedly plans to release 1-terabyte perpendicular drives in 2007. A terabyte is equal to 1,000 gigabytes.


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