Client-Server Web Apps with JavaScript and Java

Chapter 12. Virtualization

People don’t appreciate the substance of things. Objects in space. People miss out on what’s solid.

— Jubal Early (Firefly, Objects in Space)

The word “computer” immediately brings to mind some image of machinery, perhaps a monitor and keyboard, a laptop, or a stack of servers. In each case, the image is a tangible, solid, material object. This common impression is not particularly useful in software development when the physical details of hardware are masked by additional abstraction layers. Virtualization is a term used to describe a technology that hides details and specific implementation characteristics. It applies to a range of technologies related to hardware platforms, operating systems, storage devices, and network resources. While it is not directly tied to client-server web development or any other paradigm, it is interesting because many such applications are intended for large-scale deployments built on virtualization solutions. Virtualization is a powerful concept that impacts practices related to active development, deployment, scaling, and disaster recovery.

Full Virtualization

Without virtualization, a server is defined by and limited to physical constraints. Server administrators build and configure servers with a specific set of options suited to their particular hardware and purpose. Individuals on a development team each install software and configure their machine to conform to the target server. Hardware limitations, performance bottlenecks, ...