ScaleMP founder and CEO Shai Fultheim has an article today at the Virtualization Journal extolling the benefits of using server virtualization to aggregate many servers into one, rather than the usual one into many approach used in the enterprise
There is a new emerging, third kind of computing virtualization: high-end virtualization in which multiple physical systems appear to function as a single logical system. This virtualization paradigm is known as aggregation and it is basically the opposite of partitioning. The building blocks of this approach are the same x86 industry standard servers used in the scale-out (clustering) approach, preserving the low cost. In addition, by running a single logical system, customers manage a single operating system, and take advantage of large contiguous memory and unified I/O architecture.