Virtualization Overview

Virtualization is a very hot topic these days. Virtualization is a really neat technology that allows one computer which is running Linux (or another operating system) to act as multiple computers. Each of these virtual computers can run any PC operating system including other versions or distributions of Linux, or OS/2 or even Windows.

The primary attraction for using virtualization is that it allows more complete utilization of relatively expensive hardware resources. Most hardware is very powerful these days and, for the most part, is seriously underutilized as the CPU, disk and memory capacity of most server hardware today far exceeds the demands being placed on it by multiple web sites, as well as email and other types of network servers. This can be especially true in smaller companies which impose only limited demands on their servers. Virtualization allows companies to more fully utilize those available resources.

Other reasons for using virtualization include the ability to run software meant for one operating system on hardware that is running a different primary operating system. It also provides the ability to run older software which requires an older version of the primary operating system. For example I have one program that only runs on older versions of Red Hat Linux, versions that do not have all of the current security updates that it is prudent to have. So I run the most current version of Fedora, with all current security updates and I run a virtual computer with that older version of Red Hat to enable me to use that older software.

There are a number of virtualization products available and some are Open Source Software while others are proprietary. All do well for most virtualization needs but all have their quirks as well.

• Xen – a hypervisor which is part of the Red Hat Enterprise distributions. It requires especially compiled kernels to achieve best performance and functionality. Thus it is a poor choice for Windows guests.
• KVM – or Kernel-based Virtual Machine. This is a relatively new Open Source project that seems to have a large number of supporters.
• VMWare – this proprietary virtualization product provides good capabilities through a number of relatively specialized products. There is a free (of charge) “player” which allows one to run a virtual machine that has been previously created, but does not allow creation of virtual machines.
• VirtualBox – A Free Open Source product that performs very well and offers lots of capabilities.

I used VMWare for several years and was fairly happy with it. The biggest issue I had was that their support for kernel upgrades has been quite limited. I currently use VirtualBox because it seems to have better performance than VMWare and provides compatibility with all upgrade kernels. I was never happy when, after a kernel upgrade for security reasons, VMWare would no longer work, and recompiling the kernel module for VMWare failed. VirtualBox does not seem to have this problem.

Here is a short review of VirtualBox on my DataBook® web site.

Please contact us for more information about virtualization and how it might be used to help your business.