Virtualization allows you to place numerous stand-alone application servers onto a single server without sacrificing functionality. Each virtual server behaves as if it is running in its own physical system; it is unaware that it shares a physical server with other virtual servers. For this reason, it is referred to as a “virtual machine,” or a “VM.”

Why is virtualization so important? Historically, data centers dedicated one or more servers to host the applications of separate business units, because the units wanted complete control over their own infrastructures. This led to data centers full of servers running at only 5% to 10% of capacity. By turning to virtualization, data centers now can consolidate the workload and reduce their server counts (and therefore their energy and space requirements) by a factor of 10 or more while allowing business units to maintain control of their own information.

Furthermore, VMs may be quickly moved based upon fluctuating capacity requirements. Is one application suddenly bombarded by users? Switch it to a larger server with a larger capacity until the wave of activity passes. The fluidity of a virtual environment, however, means you probably have neither the ability to choose the specifications of your server nor any control over what other applications share that server with you.

Name one class of application that is suitable to run in a virtual environment. Describe the risks and benefits of hosting this particular type of application in the cloud. In addition, identify one class of application that is particularly unsuited to virtual hosting, and explain why the risks outweigh the benefits in that case.