The term “virtual” originates from the study of optics as it pertains to image reproduction. For instance, a mirror reproduces an image of an object, but because the image is not real and physical, it is deemed virtual. With this in mind, the concept of virtual machines (VMs) can be better understood. By applying virtualization software to a server, a separation between the server’s hardware and its operational ability can be achieved. In essence, the software creates a virtual “container” in which all the files of the server are duplicated and emulated. This software container or layer is called a hypervisor. With this in place, multiple virtual machines can utilize a physical server’s resources through the hypervisor even though each virtual machine may use a different operating system.

Traditionally, each physical server has its own IP address. A network accesses a server based on its IP configuration on the network. However, if that server becomes disabled, the network or portion of the network is inoperable until it can be repaired. In contrast, virtual machines have their own IP configurations, with each one having access to several physical servers that run the virtualization software. If one physical server becomes disabled, the virtual machines are thus still able to function normally by using the hardware and resources of other physical servers on the network. This high availability becomes an important issue in disaster-recovery situations.

The advantages of VMs clearly stem from the more efficient use of hardware resources, the elimination of underutilized redundancy in the IT system, and the ability to minimize downtime when servers malfunction. Larger organizations therefore enjoy greater advantages from such systems. As for disadvantages, indirect access of the physical server through the hypervisor is less efficient than direct access, and if multiple VMs are accessing a single physical server, variable performance may develop if workloads are high. While these issues may require specific attention, the advantages of virtual machines for large IT systems far outweigh the disadvantages.

For more information, see my book www.ITSurvivalGuideBook.com

22 Comments
  1. Good post as usual. I’m not sure why when increase my virtual ram on my pc it doesn’t operate as well physical ram of a much lower quantity.

    • This is an entirely differently issue from the article. That being said, virtual memory uses the hard drive to page memory which is much slower than when using actual RAM. RAM operates at speeds that a physical hard drive can’t compete with. You might be able to get a little closer using an SSD, but beyond that you’re SoL.

  2. I learn a lot from reading your post. Now i have an almost clear understanding of what virtual means and how virtual machines work. That’s really cool and amazing how we discover things like this.

  3. Interesting read. I’ve always been a fan of virtual operating systems. Because I run Windows 7 on my home computer, I like having the chance to run XP via a virtual OS. I’ve never had first hand experience with virtual servers, but I would imagine that they work in the same kind of way. This seems to make it great for emergency scenarios where the servers are at defcon 1.

  4. I’m using Ubuntu as my main OS and have tried running Windows XP on a VM. It’s a much smaller scale compared to what you explained but I do appreciate how I can run stuff on my virtual machine and not worry much about causing problems. I can just wipe my VM and start from scratch, if I need to.

  5. Before you switch to a virtual server, you definitely want to check the programs that are your mainstay and see if they will work for it or not. I was a CS rep with a tax software that was the main program for a number of offices. They switched to a virtual server then called us to know why it was not working. That was because the software needed a root drive and would frequently get confused with virtual servers. But if you can run the business necessary software on virtual, then go for it.

    • That is an excellent point. Always make sure your technologies are compatible. It should be obvious enough that it doesn’t need to be said, but obviously it does. VMs seem to be an excellent alternative, but only in appropriate settings.

      • Like many things, if you don’t plan properly, there are caveats and problems that will haunt you later on. IT is no different from other fields in that regard – if you neglect your research, you’ll end up regretting it down the road.

    • How common is it for programs to not work on a virtual server though? I have no idea if it is that common of an issue or not. How many software programs require the root drive? Not many is my guess but I am sure that you could illuminate the truth of the matter.

      • You can virtualize all physical servers, some have issues. And not all legacy apps work, especially if they have hardware dependencies. Generally speaking though, the success rate is very high and it helps extend the life and access to legacy apps by getting them off their old hardware.

  6. Virtualizing an environment can be for other reasons beyond high availability. Especially when it comes to small or medium businesses, it can be advantageous from a cost perspective to simply run a virtual host.

    The cost of running a setup that allows for high availability is often out of reach of smaller businesses.

  7. Well consider me enlightened because I knew nothing about physical versus virtual servers until the past couple days. The article above helped me understand it a little better. This is an incredibly confusing topic as I don’t have the best IT background but am trying to learn more each day. I didn’t know that virtual servers existed. I just figured that every server was physical and stacked up on top of others in a gigantic climate controlled room.

  8. It seems to me that VM’s are great especially because they minimize the downtime when a sever malfunction happens. Larger companies are out of their minds if they aren’t using VM’s! As David already pointed out the advantages for bigger IT networks far outweigh the disadvantages.

  9. I was checking about VPS and I noticed that most of them are using Linux OS. I’d guess you’d need to know more about that though before you can dive into using VPS?

  10. I would have to agree. It is good to have a virtual machine for an IT system. Thanks for educating us all on the topic.

  11. I used to say, “If you have at least 4 physical servers, it is best to virtualize.” Since the technology has matured in the area of disaster recovery, by replication procedures, I say businesses should still do it if they have only one physical server. Microsoft has helped in this area of providing 2 vm licenses with the purchase of Windows Server 2012 and Windows Server 2012 R2.
    I do not work for Microsoft, this is just an FYI. By the way, great way to explain the differences between the two.

  12. Thanks for explaining this, I am not the most tech-minded of people, but I think it makes sense.
    I didn’t realize virtual machines had access to so many different machines, but I guess that would have to be the case.

  13. In my work we use Virtual Machine for our Microsoft Exchange. This article is so true, it reduces redundancy of the equipment needed, its easy to maintain and easy to set it up unlike physical servers it can be real bulky.

  14. For something virtual, this element of information technology gives me a sense of touch. Another glorious gift to humanity, virtual machines animate parts of our lives a little. There is a sense of balance that needs proper attention from our IT managers, so it’s not only a matter of good or bad technology.

    I have heard of the virtual machines but I’ve never gotten to know its uses and advantages. It’s not commonly discussed, but we know it is important. We just did know why it is important. I particularly liked that you introduced the term “hypervisor” in your post.

  15. I dont get it? Is this like having a dedicated server vs a vp server? This is too hi tech for me.

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