HAMR time: Seagate demos terabit-per-inch hard disk technology by Sean Gallagher

HAMR time: Seagate demos terabit-per-inch hard disk technology

An image from Seagate’s patent filing for HAMR technology, showing the pattern of storage bits on a disk surface. The bits can be heated by a laser to make them more easily written to, and are more magnetically stable when cool.

Seagate is preparing the first commercial hard disks capable of storing one trillion bits of data per square inch on its platters using a technology called heat assisted magnetic recording (HAMR). That means 3.5-inch hard drives with capacities of 6 terabytes could be just around the corner—and 60-terabyte drives are that much closer to becoming a reality.

Seagate has been working with HAMR for over a decade, originally predicting storage densities of “as much as 50 terabits per square inch” when it demonstrated the technology for the first time in 2002. HAMR uses a combination of a laser and magnetic write heads that allows bits of storage to be packed more tightly together on a disk platter.

HAMR is a workaround for one of the most fundamental problems of magnetic recording media, called the Magnetic Recording Trilemma. To grossly oversimplify: packing data more tightly onto a magnetic surface requires a recording media that is more resistant to changes in magnetism—otherwise, when data is written to one bit, supermagnetic effects from the write could cause it to “bleed” over to neighboring bits, corrupting data. But in order to write to the disk effectively, the bit needs to be more easily changed.

To get around this, HAMR uses a more stable material for the storage media, but then uses heat to change that stability selectively during data writes. It uses a laser in combination with the magnetic write head to heat the bit where data is to be written.

Seagate claims to have used HAMR to achieve a data density of just over 1 trillion bits per square inch on a drive surface, and believes that it will, at a minimum be able to handle densities of up to 10 terabits per square inch within a decade. By comparison, current drives using Perpendicular Magnetic Recording (PMR) technology have a density of up to about 630 gigabits per square inch, and has a theoretical limit around 1 terabit per square inch, HAMR could theoretically reach densities of up to 10 terabit or more per square inch.

There’s just one problem with Seagate’s cheers about breaking the 1-terabit per square inch barrier: somebody already claimed that title. In October, as Ars reported, researchers at Singapore’s Institute of Materials Research and Engineering announced in October that they had developed a process that could create drive surfaces with densities of 3.3 terabits per square inch. The IMRE researchers used a technology called bit-patterned recording (BPR), which uses a pattern of bit-storing “islands” on an otherwise nonmagnetic surface instead of using traditional cylindrical “tracks” on the disk surface.

In the long term, HAMR shows more promise. But BPR’s advantage is that it uses materials and processes similar to those used to manufacture PMR drives, and can be done more inexpensively now. This is something Seagate may have an inkling of, as the company’s researchers have done a considerable amount of work on BPR technology themselves, and has patent claims on both HAMR and BPR.


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