I have a lot of my small business customers asking this question, usually after one of us from itgroove has talked about the possibilities offered by virtualization. So, at the risk of possibly offending the more technically minded out there, here is my "Virtualization 101" primer.
At the most basic level, virtualization is the ability to run a "computer on software" rather than run "software on a computer". Yup, it’s just that simple and just that complex!
All of us are familiar with running "software on a computer", in fact most of us don’t even give it a second thought. Right now I’m typing up this post on my trusty HP laptop using OneNote2010 on top of Windows7 and both are "software on a computer". In this case Windows7 is installed on the physical hardware and it supports all of my various application needs like the OneNote that I’m using to write this post. Pretty vanilla stuff.
Virtualization adds in an extra layer between the operating system (like Windows7) and the physical hardware. This extra layer, which is usually referred to as a "hypervisor", provides a software-based "hardware platform" as a target for building out one or more operating systems. Each running operating system is referred to as a "virtual machine" or "VM" as it is a computer (machine) that exists in a virtual software world rather than a physical hardware world . Depending on the type of hypervisor used, a given hardware platform can support multiple running VM’s. So, again in simple terms, virtualization allows a single physical computer to host more than one running operating system at the same time. The physical resources of the computer – CPU, disks, memory, net work cards, and so on – are shared by the multiple operating systems. Very cool stuff.
There are many virtualization vendors and many different virtualization products available in the marketplace. In the end there are really only two main methods used to provide a virtualized platform: 1) A Type 1 hypervisor which runs directly on the physical hardware and, 2) A Type 2 hypervisor that runs on top of another operating system. It can be argued that the difference between the two types is merely semantics but the differences between the two are important and the two types generally serve different and distinct user requirements.
Type 2 hypervisors have been around for a long time and, in fact, a Type 2 hypervisor actually ships with Windows7! XP Mode provides an XP VM that runs on top of Windows7. You can fire up XP Mode, install applications (software) into it and then either run them from the XP desktop or allow Windows7 to integrate them into its own desktop. As a Type 2 hypervisor, XP Mode requires services from Windows7 in order to operate, it cannot be installed directly on the physical hardware itself. Because Type 2 hypervisors are generally installed on top of a "regular" operating system they are considered to be less efficient than their Type 1 cousins (more on that in a moment). As a general rule of thumb, Type 2 hypervisors are not usually a good choice for running a number of VM’s on a single host although they usually do a fine job of running one or two VM’s. And, yes, they do consume resources from the host operating system so don’t plan on installing a Type 2 hypervisor on your overburdened and underpowered four year old server!
Aside from XP Mode some of the more popular Type 2 hypervisors available are VMware Server , VMware Workstation, VMware Fusion (Mac), Parallels (Mac) and VirtualBox from Oracle. I use VMware Workstation all the time as a lab and testing platform.
The real heavy lifting in the virtualization world is performed by the Type 1 hypervisors. The three best known Type 1 hypervisors are ESX/ESXi from VMware, Hyper-V from Microsoft and XenServer from Citrix. ESX/ESXi and XenServer are both based on Linux kernels while Hyper-V is based on the Windows Server kernel (the kernel is the essential "core" of an operating system). And, yes, I know, I just said all three are based on "operating systems", so what’s the difference between these and the Type 2’s? In simple terms, the Type 1 hypervisors are purpose built to do nothing other than provide a solid and highly-tuned "home" for VM’s — they don’t provide any of the other services expected of modern operating systems. Type 1 hypervisors are “lean and mean”! Because they are so thin and so highly tuned, Type 1 hypervisors provide far more of the physical host’s resources to the VM’s that run on top of them. It is not terribly unusual to see 6, 8, 10 or more VM’s running on top of a single physical computer.
So, how does this actually play out for the SMB? Simple! It let’s you get more bang for your buck and that speaks directly to the bottom line. All three vendors of the Type 1 hypervisors give you the hypervisor for “free” which means you can get into the virtualization game for basically the cost of the hardware and, of course, your properly licensed operating system(s). Microsoft actively encourages SMB’s to use Hyper-V to virtualize Small Business Server 2011 Premium (all of the software and licenses come with the product). Virtualization is a technology that is here to stay and it is something that you can use to leverage your hardware investment.
In future posts I will highlight how various virtualization technologies have been used within our SMB customer base to drive savings and services delivery. Hopefully, there will be some useful nuggets of information that will help you with your virtualization efforts.