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.