Server Virtualization:         

Server Virtualization is currently the most pertinent technology behind Par 4's core goal:  IT Consolidation.  We are not talking about consolidation of sheet metal here (e.g. blade servers), we are talking about reducing the amount of physical resources required to support your applications (in other words, reducing the number of processors, memory, network cards, and corresponding electricity). 

With the continuous improvements in x86 architecture, Wintel servers are now capable of supporting very heavy workloads.  The growth in processing capabilities has outstripped the application requirements by a long shot.  However, it is impractical and sometimes impossible to co-locate applications on the same server due to OS / application conflicts.  However, with virtualization software you can run each OS and application in their own instance - presenting themselves to the world just like a physical machine would.  While they are running off of the same physical server, the virtualization layer isolates and encapsulates them, thereby eliminating conflicts between them.

VMware's virtualization technology is clearly the superior product on the market and with advanced features on the horizon such as Continuous Availablity (made possible through their proprietary clustered file system), they appear to be the likely leader for some time to come.