The Building Blocks

Having looked at the overall picture in previous blog (The Evolution), lets continue digging into Virtual Machines (the building blocks)



So, what exactly is a Virtual Machine? As the name implies, you can imagine virtual machine as logical machine running on top of a physical machine. These logical machines are capable of hosting a full operating system (also called the “Guest OS”). As virtual machines are nothing but an illusion of a full real machine, this technique is also referred to as “Full Virtualization”, “Operating-system-level Virtualization”. All VMs hosted on a physical server share its resources like CPU, Memory, Disk Space, Network cards etc. Due to their ability to abstract hardware resources from users, they are also referred to as “Hardware Virtualization” or “Platform Virtualization”.

Now, this gets confusing right? As you proceed further, you will notice that there are many industry terms used to refer to such concepts. I’ll try to make it easy for you to understand the reasoning behind the technical terminology used. However, we will be only touching the surface in this series, there is a big ocean underneath if you want to dive into each of these.

As VMs are just logical systems running on top of a physical server they don’t have any hardware of their own (obviously). The application (i.e. software) running within the VM uses “virtual hardware” which in-turn maps to physical hardware on which VM runs. Now there has to be some component which maps this virtual hardware to the physical hardware. This is called “Hypervisor” or “Virtual Machine Monitor VMM”. Hypervisors are further categorised into Type1 (also known as “Bare-metal Hypervisor” ) and Type2 (also called “Hosted Hypervisor”); but we will not get into those details in this blog (however tempting it might be).
Here is a pic showing the concepts explained above.

Products in Market : Different vendors came up with their own Hypervisors. VMWare’s ESXi, Microsoft’s Hyper-V, Citrix’s Xen (I mean XenProject, not XenServer; another confusing term) are the market leaders in this space.

That’s all for now.  In next blog, we will discuss about more evolved technologies in Virtualization world (in beginners terms) and look into the nitty-gritties associated with other types of virtualizations.

Stay tuned as we continue our journey in the series – “The Science of Illusion“.
Previous blog : The Science of Illusion (Part 2) : The Evolution (Big Bang)
Coming up : The Science of Illusion (Part 3) – The World of Virtualization

Priya Saxena