From Jan 2016:
https://queue.acm.org/detail.cfm?id=2874238
For the entire careers of most practicing computer scientists, a
fundamental observation has consistently held true: CPUs are
significantly more performant and more expensive than I/O
devices. The fact that CPUs can process data at extremely high
rates, while simultaneously servicing multiple I/O devices, has
had a sweeping impact on the design of both hardware and software
for systems of all sizes, for pretty much as long as we've been
building them.
This assumption, however, is in the process of being completely
invalidated.
===
Even today, a Spark committer says that for Spark CPU is already
often the bottleneck (for decompression):
https://www.oreilly.com/ideas/investigating-sparks-performance
