Does the use of virtual machine technology always reduce complexity?

When I've had a chance to speak with executives of suppliers of virtual machine software, they often point out that one of the major benefits of deploying application environments inside of virtual machines is simplicity. That is, they suggest that using virtual machine software reduces complexity in the environment.

While that might be true from the perspective of that single application, it may not be true of the whole environment. Installation, migration from one physical machine to another and even some application management tasks can be facilitated by the use of virtual machine technology.

Installation may change from an arduous task to merely copying a file. Migration of an application environment from one physical system to another also become a file transfer.

From a broader perspective, however, virtual machine technology is another layer of technology, one that requires expertise. The fact that virtual machines running different application environments, different operating systems, etc. can all share a single physical machine may require more expertise that managing a single operating system, application, etc. on a single physical system. Organizations may find that more types of expertise are needed than before.

In a purely physical environment, one could walk through the datacenter and see all of the machines. In a consolidated datacenter where many virtual systems are supported by a small number of physical systems, all of the systems in use may be hard to find without the help of some sophisticated management software. New virtual resources can pop up in moments and disappear just as quickly.

As with other types of marketing hype, the statement that virtual machine software always reduces complexity needs to be examined closely. It may reduce complexity in one area of datacenter operations while imposing new types of complexity in others.

Do you agree? Can you think of examples in which adding virtual machine software created new stresses for the IT administrators? just as any other type of software.