Virtualization: 1 large virtual server based on 2x (or more) real

www.scalemp.com --> just what You are looking for...

On simple servers is not possible to provide acceptable latency for the processor to handle memory in another physical server, you need a communication bus with a high bandwidth.
The tyre have IBM server x3950 is called ScaleXpander Option Kit. It allows you to combine up to 4 servers x3950 one (one operating system).
\rwww.redbooks.ibm.com/redbooks/SG247630/4-2.htm
There was another server SGI Origin200, but it's RISC servers, which were connected by a similar bus in one system.

I can recommend

buzzword: cluster (cluster)

Another more intelligent word — cloud (cloud)

Why do you need 50 GB of memory? Well, for what tasks?
Some software is able to work on multiple machines "like" on one. Paid MySQL is the mode of clustering, something like that can do squid for mathematical calculations there are libraries in MP, etc.

afaik, the JVM could similarly be scaled down using the development of Terracota. but about such Axis zoom on a normal gland have not heard anything. only individual softiny sharpened by clustering. cunning or iron, with an astronomical price tag.