I've recently seen a Presentation on the issues around exascale. The end result ... EVERYTHING must fundamentally change. The power requirements would alone swallow the needs of a small town. Even DDR4's bandwidth would be a second rate solution. The scheduling requirement across the hundreds of thousands of processors could consume the system alone, much less allow it to work. Only one of the supercomputing giants is actually building systems (for five years out from now) that will scale out to past 5 petaflops and Sandia is thinking about 1,000 petaflops.

The linux weenies might as well forget it because there's no way in hell that linux could ever run a box at Exascale. The hardware alone will be more than 12 years out.