Virtualization is not a new concept, but without it, cloud services wouldn’t be possible.  

We use virtualization every time we access the cloud and cloud services. But to understand it, you’ll first need to understand what a virtual machine – or VM – is.  

What is a virtual machine? 

A physical machine is a computer, like this Windows machine we’re all familiar with. It has a CPU, memory, a hard drive and a network connection. It could also be a laptop, tablet or other device. In the context of virtualization, the physical computer is called a ‘host’. 

Virtualization is the process of using special software on a physical machine – the host – to create virtual machines. This special software is called a hypervisor and a virtual machine is called a ‘guest’. Modern virtualization tends to be hardware-based rather than software-based, which means we can use the host resources more efficiently. 

A virtual machine is really just a file sitting on the hard drive and to users it appears and acts no differently to a physical computer. It can be configured to use any operating system with any amount of things like CPU capacity and storage space from its host. The only limit to how many virtual machines can be created and run is the host CPU, RAM and other resources. RAM especially is almost always the main limiting factor.  

So together, all the virtual machines share the same resources of the host, but each virtual machine works independently of each other. 

How does virtualization work? 

Imagine a data center containing a large number of servers, each running a different application.  

Some servers aren’t being used to their full capacity because the demand for that particular application is low, or the server capacity exceeds the potential demand. However, there’s still the associated cost of energy and resources to run the server, maximise its uptime, keep it updated and prevent it from crashing or overheating. 

Virtualization eliminates this waste by enabling cloud providers (or any organization for that matter) to virtualize – or consolidate – the physical servers into fewer, more powerful and energy efficient servers. A virtual machine can then run separate operating systems and applications which are all installed on one physical server. Multiple virtual machines can run at the same time and share the underlying hardware resources, so they’re utilizing them much more efficiently. 

This sharing of hardware resources is achieved through the hypervisor, which creates the virtualized environment, enabling multiple virtual machines to run on the same host.  

The hypervisor sits between the physical server hardware and the virtual machines and creates a shared pool of virtual hardware resources for each of them to access. Any request to the hardware goes through the hypervisor, which ensures the resources are shared between all the virtual machines as they’re needed.

Benefits of virtualization 

Virtualization provides the basis for cloud services because it allows providers to optimize their resources, which enables utility pricing and on-demand services.  

Cost effective 

There are obvious cost benefits of virtualization including reduced capital expenditure – less hardware’s needed because multiple virtual machines can run on a single host. And operating costs are lower because less space, power and cooling is required in the data center.