Magnetic "wobbles" cause disk failure

New research could lead to more reliable hard disks

Scientists have discovered one of the major causes of hard disk failure.

According to researchers working at the University of California and Hitachi Global Storage Technologies, understanding certain types of disk drive failures, called magnetic avalanches, could help disk drive manufacturers produce more reliable storage.

Magnetic avalanches occur when a magnetic head hovers over a patch of disk drive causing the polarity of that part of the drive to change its alignment or spin. The patch's polarity in many magnetic materials changes in a haphazard series of large and small jumps that physicists liken to an avalanche - though the scientist's research showed it often behaves more like an explosion or runaway fire. These avalanches can cause sections of hard drive to lose data.

Research was carried by Joshua Deutsch, professor of physics at the University of California, Santa Cruz, and Andreas Berger, who did the research while at Hitachi Global Storage Technologies.

Deutsch said that the research paper, published in 13 July edition of Physical Review Letters, that the findings advanced knowledge of magnetic spin in drives.

"The big advance in this paper is that in previous models of avalanches, the spin just flips from up to down as soon as they apply a magnetic field, and they're done. But that's not the way spin behaves in the real world," Deutsch said.

The scientists said that previous models overlooked an effect called "spin precession", which each magnetic field exerts on its neighbours. The scientists likened each individual bit of information on a platter to a "tiny pincushion bristling with individual magnetic fields."

As the head of the drive nears, each pin wobbles in a widening circle - pointing neither up or down but somewhere in between - before it settles on its new polarity. They called that wobbling "precession" and said it resembled the way a spinning top draws out circles as it rotates.

"It takes around a few nanoseconds for a precession to die down," said Deutsch. "That's not that fast compared to computers today. It's not as fast as the timescale you get for a transistor to switch." During that brief time, each magnetic field contributes forces that affect the precession of neighbouring fields. Each of these spins

Combining all those wobbles adds up to a lot of energy that changes the polarity of neighbouring bits and spreads across the surface, causing sections of disk drive to be wiped out.

The researchers suggested that the reason these avalanches die out is that the magnetic material can dampen the wobbles. They said that materials that good damping abilities would make candidates for use in hard drives.

"Obviously, disk drive makers have already learned by an enormous amount of ingenuity and trial and error what materials make good disks," Deutsch said. "But now we understand a lot better one of the reasons why - because the materials are good at damping, and we can quantify how damping will stop runaway avalanches. We still can't calculate their damping, but at least we can measure it."

True random number generator goes online

A 'true' random number generator that relies on the unpredictable quantum process of photon emission has gone online providing academic and scientific community access to true random numbers free of charge.

A group of computer scientists from Ruder Boškovic Institute (RBI) in Zagreb, Croatia, developed and launched the Quantum Random Bit Generator Service (QRBGS) whose range of applications spans fields as diverse as advanced scientific simulations, cryptographic data protection and security applications, as well as virtual entertainment – including online gambling and computer games.

Ordinary random number generators found in most computers in use today are 'pseudo-random' numbers that use various algorithms to pick the numbers from large pre-compiled databases of numbers obtained by methods such as rolling the dice.

Anyone who has access to such a database from which the pseudo-random number is picked, can accurately predict the next number that comes out of such generators.

But, the 'Quantum Random Bit Generator' (QRBG121), which is the engine for QRBGS, is a fast non-deterministic random bit (number) generator whose randomness relies on intrinsic randomness of the quantum physical process of photonic emission in semiconductors and subsequent detection by photoelectric effect.

RBI’s service enables real-time internet access to QRGB device through several network access modes, such as C/C++ libraries, web services and Mathematica/Matlab client add-ons.

The QRBG device itself is located and operated at the RBI and is connected to the internet through advanced computer technologies such as computer clusters and GRID networks.

The Psychology of Social Computing: What Best Explains the Success of Facebook?

Facebook has been getting a lot of UK press of late, from consideration of how much it is worth, to privacy issues, universities getting annoyed at students using it to criticize staff, being censored by organizations frightened of it, and the musings of BBC journalists about whether people are too “old” to Facebook.

What makes Facebook such an attraction? Some theories… more

Those OS X iPods? They're Already Here! Pixo, ARM, and the Mac OS

Speculation has run rampant over how Apple might bring iPhone technologies to its iPod line. Will the next generation of iPods look like the iPhone and run the same software? It turns out I stumbled upon the answers six months ago. Now I've discovered additional proof. You’ll be surprised to find that much of what we all thought we knew about the iPod was wrong. -read more from..

Developing QuickTime Applications for the iPod

It's commonly believed that Apple's iPod portable music player uses a bare-bones operating system developed by a company called Pixo, Inc., and that the device itself is a closed system insofar as only Apple can add software modules -- such as the games or contacts list manager -- to the device. And, it's further believed, even if there were a way to load third-party applications onto the device, actually writing such applications requires access to development tools whose availability is tightly controlled and that are expensive to license. In effect, the iPod is even less open than the original Macintosh computer (which is to say, not very open at all).

In fact, none of these beliefs is true. Once we know what's going on, it's fairly simple to develop quite powerful applications for the iPod using nothing more than a text editor and a programming language that most of us had considered to be long since obsolete. In this article, I'll show just how easy it is to write iPod applications by developing an application that can open and display QuickTime movies on the iPod. In addition, I'll show how to support the standard editing operations (cut, copy, paste, and undo). The result will be an iPod-based version of our QuickTime sample application, QTShell. For reasons that will become clear soon, let's call this application "SnoEez". Figure 1 shows a frame of a movie being displayed by SnoEez. (You may recognize this as a cropped version of our standard penguin movie, with the X-ray video effect applied to the entire movie.) more ..