More virtual, less machine

A virtual machine, in the end, is really an elaborate game of "let's pretend". The host system (often called a hypervisor), persuades an operating system that a physical machine exists, and the operating system works "as normal", driving video cards that do not really exist and responding to timer interrupts created by the hypervisor.

Our initial use of virtual machines was to duplicate our physical machines. Yet in the past decade, we have learned about the advantages of virtual machines, including the ability to create (and destroy) virtual machines on demand. These abilities have changed our ideas about computers.

Physical computers (that is, the real computers one can touch) often server multiple purposes. A desktop PC provides e-mail, word processing, spreadsheets, photo editing, and a bunch of other services.

Virtual computers tend to be specialized. We build virtual machines often as single-purpose servers: web servers, database servers, message queue servers, ... you get the idea.

Our operating systems and system configurations have been designed around the desktop computer, the one serving multiple purposes. Thus, the operating system has to provide all possible services, including those that might never be used.

But with specialized virtual servers, perhaps we can benefit from a different approach. Perhaps we can use a specialized operating system, one that includes only the features we need for our application. For example, a web server needs an operating system and the web server software, and possibly some custom scripts or programs to assist the web server -- but that's it. It doesn't need to worry about video cards or printing. It doesn't need to worry about programmers and their IDEs, and it doesn't need to have a special debug mode for the processor.

Message queue servers are also specialized, and if they keep everything in memory then they need little about file systems and reading or writing files. (They may need enough to bootstrap the operating system.)

All of our specialized servers -- and maybe some specialized desktop or laptop PCs -- could get along with a specialized operating system, one that uses the components of a "real" operating and just enough of those components to get the job done.

We could change policy management on servers. Our current arrangement sees each server as a little stand-alone unit that must receive policies and updates to those policies. That means that the operating system must be able to receive the policy updates. But we could change that. We could, upon instantiation of the virtual server, build in the policies that we desire. If the policies change, instead of sending an update, we create a new virtual instance of our server with the new policies. Think of it as "server management meets immutable objects".

The beauty of virtual servers is not that they are cheaper to run, it is that we can throw them away and create new ones on demand.