[ChuckMcM]

It is exactly the Beowulf vs Mainframe problem. And it is this: "Some things do only work on SMP, because for some workloads no network fabric (that I know of) is as fast as the system bus." is under siege.

From a systems architecture point of view it is a really interesting exploration of Amdahl's law. So many things that people said "You'll never do that on a networked cluster of machines." have fallen (data bases being one of the larger ones). And while it used to be mainframes won on I/O channel capacity, Google and others have shown that when you can parallelize the I/O channels effectively that advantage goes away as well.