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ENGINEERING WITH A MISSION: 100 YEARS

Thanks for the Memory

Flash can't get any smaller. The future lies with shingled magnetic.

Flash memory—tiny, fast, and rugged—is gradually replacing magnetic memory in laptops, smartphones, and other consumer devices. But for the growing quantity of data being stored in the cloud, says Ahmed Amer, professor of computer engineering, the future still lies with magnetic memory, which holds much more data—for much less money.

There’s just one small difficulty: Computer technology’s inexorable drive toward tinier, denser memory devices is about to send magnetic memory crashing into a brick wall.

Engineers have been so successful at miniaturizing magnetic memory that they can now squeeze 100 billion bits of data into each square inch. But there’s no more room to shrink: The magnetic bits encoding the 0s and 1s consist of only a few molecules each, and if they were to get much smaller, the natural jiggling of atoms at room temperature would be enough to destabilize the bits.

“Pushing magnetic memory further means pushing against the fundamental laws of physics,” Amer says.

To deal with this problem, engineers are working on a new technology called “shingled magnetic memory” built from materials that are more stable—that is, less jiggly—than the iron oxide particles used in standard magnetic memory. Bits of data written on these materials can be smaller without the data getting lost to “jiggliness.”

There’s a downside, however, to this stability. To write a bit of data onto such stable material requires a powerful magnet with a large magnetic field, and such a magnet can write only large bits. Writing data in shingled magnetic memory is like trying to execute a fine pen-and-ink drawing using a thick paintbrush.

Nevertheless, there is a way around this apparent conundrum: The device paints each thick new line of data over the previous line, allowing only a tiny sliver of the previous line to show—resulting in a structure like a shingled roof.

This shingling creates a challenge for the device’s operating system, which can’t write over a bit of memory without erasing the bits shingled over it. That’s where operating system software designers such as Amer come into the picture.

“This technology could help take us beyond a terabit—a trillion bits—per square inch,” Amer predicts.