A few decades back I was working at Goddard Space Flight Center. I'm sorry to say that I left just before some people I'd met, Don Becker and Thomas Sterling, built the first Linux cluster, Beowulf. They didn't know it, but by making a cheap cluster from 16 486DXs processors and 10Mbps Ethernet, they were creating the ancestor to today's Linux supercomputers. Now, not 20 years later, well over 90% of the world top 500 supercomputers are running Linux.
The new supercomputer champion of champions, according to the TOP500 list of the world's top supercomputers is Sequoia. This IBM BlueGene/Q system installed at the Department of Energy's Lawrence Livermore National Laboratory achieved an impressive 16.32 petaflop per second (Pflop/s) on the Linpack benchmark using 1,572,864 cores." That's 16.32 quadrillion floating-point operations per second). The operating system? Linux of course.
Second place goes to Japan's Fujitsu's "K Computer." It's installed at the RIKEN Advanced Institute for Computational Science (AICS) in Kobe, Japan, with 10.51 Pflop. It uses 705,024 SPARC64 processing cores. The hardware may be Sun/Oracle in design, but the operating system is Linux, not Solaris or OpenSolaris.
Indeed, Solaris isn't on the top supercomputer list at all and OpenSolaris only has one system. Microsoft does a little better than that. There are two top 500 supercomputers that run Windows HPC 2008. The only operating system that even pretends to give Linux any competition if IBM's house brand of Unix: AIX with 22 systems, aka 4.4% of the world's fastest supercomputers.
If you just glance at the Top 500 chart you might be fooled into thinking Linux isn't quite as dominant as it really is. If you look closer though you'll see that after AIX instead of the customized Linux that makes up the bulk of the list, there are numerous specific Linux distributions. At the top of this list you'll find SUSE Linux Enterprise Server 9 with 11 systems; SLES 10 with 8; and Cray Linux with 7. The supercomputer world really does belong to Linux.
What's even more amazing than Linux's total domination of supercomputing is how fast these Linux-powered thinking machines are getting faster. Only six-months ago, in the last round-up of supercomputers, the combined performance of all the supercomputers was 74.2 Pflop/s. Now, the total performance of all the systems on the list is 123.4 Pflop/s. Can you say fast? I knew you could!
To look at another way, 20 of the supercomputers on the latest list reached performance levels of 1 Pflop/s or more. The first supercomputer to break the petaflop barrier, IBM's RoadRunner running Linux of course, only did it in 2008 The No. 500 machine on the list? Its 60.8 teraflop/s would have made it number 332 last year.
Looking ahead, the next goal to crack will be exaflop supercomputers (PDF Link). An Exaflop is a thousand petaflops.
Since Sequoia just cracked 16 Pflop/s that may sound like a goal for the 2020s or even the 2030s. Intel thinks it can get supercomputers there with its new Xeon Phi processor family by 2018. I'm not sure they'll be able to do it that fast. I do know though what operating system the first exaflop capable supercomputer will be running though. It will be running Linux.