If you want a really, really fast computer, there are all kind of ways to build the hardware architecture, but one thing that almost all of them have in common is that they run Linux. The top spot now appears to belong to the Tianhe-1A , which means "Milky Way," at a research center at the National University of Defense Technology (NUDT) in Tianjin, China.

I say "appears" because the official Top 500 Supercomputer List won’t be out until early November. Still, according to a New York Times report, Jack Dongarra, the University of Tennessee computer scientist who maintains the Top 500 ranking, said, the Tianhe-1A "blows away the existing No. 1 machine," which is a Cray XT5 Jaguar at the National Center for Computational Sciences. Dongarra concluded, "We don’t close the books until Nov. 1, but I would say it is unlikely we will see a system that is faster."

How much faster? NUDT claims the machine is 1.4 times faster than Cray XT5 Jaguar. NUDT claims that the computer’s peak performance can hit 1.206 petaflops and jogs along at 563.1 teraflops. To do this, the Tianhe-1A system covers a square kilometer, weights in at 155-tons and uses 14,336 Intel Xeon CPUs and 7,168 Nvidia Tesla GPUs.

The software behind it? Linux of course. Linux has long been the operating system of choice for the world’s fastest computers. While NUDT hasn’t said which specific Linux they used, I strongly suspect it’s a high-speed optimized version of China’s Red Flag Software’s Red Flag Linux.

It’s not just supercomputers that have become Linux fans. Other high-speed, no-room-for-failure systems have moved to Linux. The one that comes first to my mind is the London Stock Exchange, which dumped its slow Windows/.NET system for Linux. It’s not the only one. Many of the world’s stock exchanges, where every millisecond counts, have either already switched to Linux or are planning on it.

The bottom line: when speed and reliability is what you have to have, Linux is the operating system you have to use.

A version of this story was first published in ComputerWorld.