James Robert Kelley

Virtualization solves many problems in modern server environments. Often a dedicated server is required for a specific application, which may be designed in a way that will interfere with other applications on the same server. Virtualization decreases the cost of such applications by reducing the hardware required to run the application. With VMWare or Xen an existing server can run a dedicated OS inside of a Virtual Machine.

Virtualization can be used successfully for projects that require a dedicated OS, server consolidation, or for running temporary machines for testing or short term projects. Virtualization can also greatly enhance redundancy and recovery from disaster. The Virtual Machines can easily be moved to another physical machine without the timely process of reinstalling the server OS and applications.

While all of this is very exciting, there are times when Virtualization is not appropriate. For example, you do not want to over-virtualize by installing a new Virtual Machine for each and every application. A VM requires a base Operating System, which consumes memory and processor time. If a single application needs to be added to a server, it would not make sense to consume the resources if the application “plays well” with the other applications on the server.

Another time Virtualization is not appropriate is when the server requires specialized hardware. The VM environments handle typical hardware very well, such as mice, keyboards, network cards, etc. More specialized hardware, such as telephony boards do not have direct support. VMWare provides to the virtualized OS an interface that appears to be a generic device. You may have a highly advanced network card that requires a special driver, but the VM will see the card as a generic AMD network card. This allows for portable, easy and standard OS installation on Virtual Machines, at the cost of direct control over the device.

Applications that require high speed interaction with hardware, even generic devices, is not appropriate for a VM. Some applications require highly precise timing, or the ability to pull packets off of the wire at high speed. These applications cannot be optimized with the hardware, since they are not aware of the underlying hardware.

Keep in mind the requirements of the application when deciding whether to virtualize, if you are running a web application, additional Domain Controller, or you are wanting to consolidate ancient hardware onto a more stable platform; Virtualization may be the way to go.