While the hard-drive industry has been using longitudinal recording successfully for five decades, it is now within two product generations of reaching its practical limit.For about the past decade, scientists and engineers have pondered the potential effects of a natural phenomenon called superparamagnetism and postulated when its presence might interfere with the progress of the hard-disk drive, or HDD, industry.
Since the first commercial hard drive was introduced, in 1956, the industry has grown storage capacity exponentially by decreasing the size of the magnetic grains that make up data bits. In effect, the smaller the magnetic grain, the smaller the bit, the more data that can be stored on a disk. With longitudinal recording, we are getting close to the point where data integrity will be harmed if we continue to shrink the magnetic grains. This is due to the superparamagnetic effect.
Superparamagnetism occurs when the microscopic magnetic grains on the disk become so tiny that random thermal vibrations at room temperature cause them to lose their ability to hold their magnetic orientations. What results are "flipped bits" -- bits whose magnetic north and south poles suddenly and spontaneously reverse -- that corrupt data, rendering it and the storage device unreliable.
Today, the hard-drive industry's ability to push out the superparamagnetic limit is more critical than ever as capacity requirements continue to grow dramatically. This is due, in large part, to the increasing use of hard drives in consumer electronic devices and the desire to pack more and more storage capacity on smaller devices. The superparamagnetic effect on current magnetic recording technologies will make that growth impossible within one-to-two years.
| The superparamagnetic barrier is drawing nearer, forcing the industry to slow the historically rapid pace of growth in disk drive capacity. |
To help understand how perpendicular recording works, think of the bits as small bar magnets.
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