How does server virtualisation work?

Optimal use of resources, reduced costs and less hardware is just part of what server virtualisation has to offer. If you’re interested in server virtualisation, you have three options to choose from: full virtualisation, para-virtualisation and OS-level virtualisation. Keep reading to find out what server virtualisation is, how it works and how it can benefit your business.

Dedicated physical servers that perform specific tasks have a fixed operating system and clearly defined storage and computing capacities. The disadvantage of individual physical servers in a data centre is that they tend to require a lot of space, maintenance and energy. Servers that are assigned a single task or application can’t share hardware and operating systems with other applications, and they usually can’t complete multiple tasks at once. Server virtualisation can be a solution to these problems.

Rather than adding to your IT infrastructure with additional physical servers, server virtualisation allows you to divide your existing hardware resources into several different virtual environments that can be used independently of each other. That way capacities can be better used without any changes to the infrastructure. With virtualisation, you can run multiple applications at the same time and use several differently configured operating systems on a single physical server. The virtual servers work separately from each other, prevent idle time and make optimal use of existing resources. This means that you’ll profit from energy- and cost-saving server consolidation.

Server admins use special virtualisation software to divide a physical server into independent instances and environments. This software enables several virtual servers to run separately from each other. This means that each server can use its own operating system and applications and can execute tasks independent of the other virtual servers.

The virtual instances that result from server virtualisation are referred to with different names, including virtual private servers (VPS), containers, guest systems and emulations. Virtualisation usually results in the masking of physical server resources such as operating system and processors. Whether physical resources are hidden from the virtual servers by the virtualisation software or are visible to all virtual servers will depend on which type of virtualisation is used. We’ll dive into the three different types of server virtualization at the end of this article.

It’s relatively easy to understand how server virtualisation works. Setting up virtualised servers works as follows:

The first step is to choose a server for your virtualisation project. Usually this will be a single dedicated server that you would like to use resources more effectively and process workloads better. Next, you’ll need to do a review of the memory, processors and hard drives being used, so you can determine how much capacity is available for one or more virtual machines. That way you can evaluate how many virtual instances you’ll have and how much computing power they can offer.

The virtualization itself is usually managed using a special hypervisor software like Hyper-V by Microsoft, vSphere by VMware, or PlateSpin Migrate. A hypervisor will take care of the partitioning of your existing hardware and software. There are two types of hypervisors:

• Type 1: This type works directly on the server as a bare metal hypervisor (for virtual machines, for example).
• Type 2: This type works on the software level with the host operating system (usually best suited for test environments).

Virtualization and partitioning can be used to create virtual applications, storage, resources, servers and other virtual networks.

Professional server virtualisation comes with a number of benefits, many of which boil down to reduced costs and energy use. Since virtualisation doesn’t involve acquiring, setting up and maintaining additional physical servers, users will benefit from flexibility and scalability. Your existing capacities can be used more effectively thanks to the optimal use of resources and increased capacities that come along with virtualisation. Workloads are distributed across virtual servers and managed in parallel without idle time.

When it comes to security in data centres and cloud security, virtual servers offer a clear disaster recovery advantage, thanks to simple data recovery and back up procedures. And because virtualised servers are isolated from one another, they are also less open to attack.

Additional advantages of server virtualisation include:

• Update installs go much more quickly, since all the servers are contained within a single physical system.
• Web hosting is simpler and more affordable.
• Data and processes can be outsourced to a private or public could, depending on the type of company and type of virtualisation involved.
• Virtual test environments can be used to test new applications and software tools.
• Live migration of systems is easier and less prone to downtime, thanks to relocated work processes.
• Networks and computing capacities provide higher fault tolerance, high availability and freedom from unplanned downtime or idle time.
• Virtual instances and environments work independently of each other, which leads to more efficient business processes.

In addition to all these advantages, there are also a number of disadvantages and risks that come along with server virtualisation. The biggest is the high start-up costs involved, coming from virtualisation software and IT experts. However, when compared with the acquisition and maintenance costs of physical servers, this disadvantage becomes rather negligible.

While it’s true that virtual servers that operate separately offer more security, you shouldn’t underestimate the risk of attacks on your virtualisation platform as a whole. This is especially true if data from multiple clients is located on virtual servers in a single physical environment.

Additional disadvantages include:

• Depending on which virtualisation software you use, you’ll have licensing fees (vendor lock in).
• Very large workloads might lead to increased use of memory and other capacities.

There are three different types of server virtualisation.

With full virtualisation, a hypervisor software (also referred to as a virtual machine monitor (VMM)) will communicate directly with the memory and CPU of the server. The software manages, coordinates and oversees the virtual servers and instances in the physical system, in order to isolate them based on the host/guest principle and keep them independent of each other. This means that guest instances won’t know that they’re not using physical resources. A number of physical resources are masked so that virtual servers and guests don’t know anything about each other. The hypervisor also manages the division of virtual resources. With full virtualisation it’s important to keep in mind that the hypervisor itself requires physical resources.

VMMs are also used for para-virtualisation, but, unlike with full virtualisation, instances are not hidden from each other. The physical network works as a single entity. Since physical resources aren’t masked, guest instances and virtual machines are aware of the required computing power.

Hypervisors aren’t used for this type of server virtualisation. The integrated virtualisation function of the operating system in question will take care of the coordination and implementation of the virtualisation. The downside of this is that all virtual servers then have to use the same operating system.

If you’re looking for alternatives to virtualising your own physical server, take a look at cloud computing and distributed computing. These solutions ensure that you won’t have to worry about physical data centres and servers and can save money by outsourcing your IT resources to the cloud in separate, high-performing architectures. You’ll get software, hardware, computing capacities and storage as a virtual service in the spirit of XaaS.

Other alternatives to virtualisation include:

• SaaS (Software as a Service)
• PaaS (Platform as a Service)
• IaaS (Infrastructure as a Service)

Server virtualisation is kind of like a Mary Poppins bag that’s able to hold much more inside it than its appearance suggests. Similarly, virtualised servers allow physical infrastructure to be scaled up internally, rather than spending money and time on increasing physical IT resources. Additionally, web hosting services can be provided efficiently and economically. Rather than using just a fraction of server capacities and distributing workloads unevenly across servers in a network, server virtualisation increases effectiveness and productivity. Managing the server centrally also increases security and data protection.