[BBLISA] PE2950 and Linux virtualization

[Scott R. Ehrlich]

What are people's experiences with CentOS 5.0 64-bit installed on dual 3 Ghz 
quad-core PE2950 systems with 32 GB RAM each, high-performance computing 
(applications that tax both the CPUs and RAM), not currently in a Beowolf 
cluster but could adapt to that, and doing so with VMWare or other 
vitualization software vs activity being done directly in the OS?

How much of a performance hit, or gain (I'd presume hit), does virtualization 
cause an application, resulting in what percentage poorer or better (I'd 
presume poorer) performance vs dealing directly with the OS?

It would be nice to have a VM perform some work, and if a person's code or 
application breaks, have it take down a VM while keeping a machine up, and not 
affecting other people's work.

It may also depend on if an application or code is written directly with/for 
the physical cpu/hardware vs more general use (VM).

Thanks for insights and experiences.

Scott