I found this article while doing some research. I knew Linux was prevalent in the webserver world. Most of the web servers out in the world run on Linux so I wasn't surprised to see this, but it is still very interesting to know that 19 out of 20 of the world's supercomputers run a variant of Linux.
Linux usage among the top supercomputers
When we list the OS for each of the top 20 supercomputers, the result for Linux is very impressive:
19 of the top 20 supercomputers in the world are running some form of Linux.
Thatâ€™s 95%! And if you just look at the top 10, ALL of them use Linux. The ratio may change a bit if you look at the complete list (it has 500 entries) but we simply didnâ€™t have time to go through the full list and find out the OS for each computer. However, there can be little doubt that Linux is a dominant OS among the top supercomputers, and most likely across the field. (Update: Linux has an 88.6% share of the top 500 supercomputers.)... the full story is right here The triumph of Linux as a supercomputer OS | Royal Pingdom