Bending the laws of physics to increase storage capacity

Scott Lowe describes the latest technology that seeks to increase hard drive capacity and meet the challenge of flipped bits. Find out what HAMR is and how it seeks to change the storage game for tomorrow's hard drives.

If you've watched the storage market at all for the last ten years, you've seen a serious inversion in the relationship between price and capacity. In short, today's hard drives pack a whole lot more punch for a whole lot less green. At the same time, however, the capacity available has only barely kept up with the demand. While hard drives have increased exponentially in size, so has the need for that additional storage space. Seagate is hard at work on a technology with the acronym HAMR (Heat-Assisted Magnetic Recording), which promises to change the way data is recorded by introducing new media and allowing for greater data density. First, though, let's take a look at the current set of challenges for increasing storage capacity in tomorrow's hard drives.

The problem of physics and flipped bits

Hard drive manufacturers have had to find new ways to record information to hard drives in order to keep up with the pace while, at the same time, continuing to obey the laws of physics. Manufacturers have recently introduced hard drives that use one such method: perpendicular recording. If you imagine bits of data as dominos lying flat on a hard drive platter, you're getting a reasonable picture of how data used to be stored before the days of perpendicular recording. Now, imagine those same dominos standing up on end. You can probably see how aligning data in this fashion—perpendicularly—can result in more data stored in a smaller amount of physical space.

Even with such advances, newer methods are needed to record data. As it is, hard drive storage technology will eventually succumb to the superparamagnetic effect. This is a physics phenomenon that limits how much data can be crammed into a small space. The superparamagnetic effect is the result of the use of very fine particles that, when small enough and packed closely enough together, begin to lose their ability to hold their magnetic orientation at room temperature, resulting in flipped bits. Flipped bits = lost data = useless storage.

Each bit of data on one of today's hard drives is made of up 50 to 100 or so grains, comprised of cobalt/platinum. While researchers have worked to lower the number of grains that represent a single bit of data (thus increasing data density) by using current recording methods and materials, going below about 50 grains per bit results in drives with much less reliability. Lowering reliability would be a huge step backward for storage manufacturers.

HAMR-based hard drives

Seagate's HAMR technology seeks to reduce the number of grains that represent a single bit of data—from 50 to just a single grain. When used in conjunction with a new media material that increases the stability of the magnetic field, HAMR can potentially increase storage densities to as high as 50 GB per square inch. However, today's materials and hard drive recording equipment cannot continue to support drastic increases without falling victim to superparamagnetism.

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Where HAMR could really change things is in the data recording process. The media layer on a HAMR-based hard drive will be made of new materials that are more stable at higher densities, but current hard drive heads will not work with the new material and are not precise enough to manipulate a single grain of magnetic material (which will ultimately represent one bit of data). Instead, the writing mechanism of tomorrow's hard drive will sport an extremely fine laser that very rapidly heats up the surface of the storage material, better preparing it for the data bit to be recorded. The data will still be written by a magnetic write head, but in a more exacting way. The material will then cool down very quickly, helping to stabilize the bit stored on the medium.

We aren't likely to see HAMR-based hard drives for a few years, but this type of research and product development shows the great lengths that hard drive manufacturers go to in order to continue to provide ever more spacious hard drives, while continuing to obey the laws of physics.

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