Recent technology trends in high-speed/low-latency local area networks has
lead to a convergence of hardware in massively parallel processors (MPPs)
and Networks of Workstations (NOWs). Relative to traditional MPPs, a NOW
offers the potential for better cost-effectiveness, increased scalability,
and decreased hardware and software development time. The main
differentiating point between NOWs and MPPs will soon be the operating
system software. 

Our system, called GLUnix, is built as a layer on top of existing
operating systems. This strategy makes the system quickly portable, tracks
vendor software upgrades, and reduces development time. Our work is an
example of "higher-order" systems research where new systems can be built
quickly by mapping new services onto the functionality provided by the
layer beneath. 

see: http://now.cs.berkeley.edu