Carnegie Mellon University

Data Storage Systems Center

College of Engineering

disk drive

November 20, 2017

Powerful storage, tiny space

Imagine a building the size of the entire city of Chicago, filled with rows and rows of hard disk drives. That’s what a big data storage center would have looked like twenty years ago. Thanks to improvements in storage technology, data centers have scaled down to the size of a football field. But there’s still a great need to shrink the size of storage technology while the amount of data increases.

Jimmy Zhu, ABB Professor of Electrical and Computer Engineering and director of the Data Storage Systems Center at Carnegie Mellon University, is one of the reasons data storage technology has come so far. Zhu is the inventor of microwave-assisted magnetic recording technology (MAMR), an extremely powerful method for storing information on hard disk drives. 

“You need data. You need a place to store data, you want to store more of it, and you also want to be able to compute it more efficiently. Those are the kinds of problems we’re working on,” said Zhu. 

Now, industry is following Zhu’s lead. Western Digital Corporation, one of the world’s leading storage drive manufacturers, debuted its new hard disk drive that may meet the storage needs of the future—using Zhu’s MAMR technology.

Zhu invented MAMR in 2007 when he discovered a way to use a magnetic charge to write data to a disk. The surface of a hard disk drive is coated with a 10 nanometer thick film of magnetic material. That film contains grains and each grain stores a charge corresponding to the ones and zeros of the data.

MAMR is novel because it uses a tiny magnetic element to emit a high frequency magnetic field that helps write data to a disk at a storage density much higher than ever before. Other techniques use heat to store information. But with MAMR, you can target only the magnetic properties of the material and write more information to a disk without worrying about reliability issues.

“Instead of using heat, you use a magnetic field that only works on the film’s magnetic moments,” said Zhu of MAMR. “It only injects energy to the magnetic bits. It’s called magnetic resonance, a similar sort of resonance as MRI.”

Here’s how MAMR works: a direct current flows through the nanoscale magnetic element, called a spin torque oscillator, that extends above the disk. The current consists of spinning electrons that generate a high speed magnetic rotation at a microwave frequency in this nano-element. The microwave field resonates with the magnetic grains in the disk and enables data to be recorded to small and energetic magnetic grains.

With this technique, the new HDD can store up to 40 TB—almost four times the storage amount of current HDDs. Zhu sees this as a real accomplishment, but continues to think about the future of storage technology.

“For a professor, to research and then get to see that research used in every Data Center is huge,” said Zhu. “That’s the wonderful thing about research. You can't guarantee there will be success, but if you don't try, you'll never get there!”