Hypervisor

Alsoknown as a virtual machine monitor, the hypervisor is software used to run different operating systems on the same computer and at the same time, using virtualization techniques.

Definition of hypervisor

We can define the hypervisor as that element that allows, thanks to virtualization, to create virtual hardware on which to run an operating system while another runs on the real hardware.

Characteristics

The main features of the hypervisor are:

• It ensures that a computer is not underused because thanks to virtualization it allows a single computer to simultaneously run different virtual machines , each with its operating system, thus optimizing the use of its resources.
• Generally the hypervisor is software .
• In some devices such as mobile phones, the hypervisor is  integrated .
• It separates the operating system from the physical machine as it will run in a virtual machine.

What is a hypervisor for?

• Provides virtual hardware for virtual machines to run.
• Manage and control the virtual machines that have been created.
• It reduces the demand for physical servers by being able to perform practically the same tasks in a virtual server.
• As a consequence of the above, it also reduces operating costs .
• And it also helps improve the use made of the surface area that houses the data center.
• It is achieved that a program that is running on a virtual server has no impact on programs on other virtual servers.
• It makes the installation of a new virtual server much faster , since you can have a template and easily duplicate it.
• It achieves that different operating systems can be run at the same time on the same computer , even if they use different technologies (Linux, Windows …).

History

The origin of hypervisors dates back to the 1970s when,  IBM , came up with a solution that would allow companies to reduce their costs considerably. Thanks to the hypervisor, a  company  that, until now, had several computers distributed throughout the different areas of the company, could now have a single much more powerful computer that would offer service to those areas .

This solution also allowed the computer to have different operating systems that worked redundantly , so that if one gave an error and stopped working, the others could continue working. In this way, reliability, solidity and efficiency were gained as work was prevented from being interrupted.

With the entry of new suppliers and the advancement of technology it has managed to simplify the code needed for virtualization and performance of it has improved exponentially.

Among the providers that came into play, Unix stands out , which at the beginning of the 21st century opted to sell hardware that stood out for being already virtualized and for being highly efficient , the problem was that its cost was very high.

Currently, it continues to seek to further improve this technology in order to make it even simpler and more accessible , especially with regard to administration.

Types

Currently, there are several types of hypervisor that can be classified as follows:

• Type 1 hypervisors:  they run directly on top of the hardware . They are known as native or “bare metal” hypervisors . Some examples of this type of hypervisor are: Oracle VM Server for x86, Xen and Microsoft Hyper-V.
• Type 2 hypervisors : these are run on top of the operating system and are known as hosted hypervisors . Here, the host operating system runs on top of the hardware while the guest operating system will function as one more program (the hypervisor manages to separate one from the other). In this case we have the following hypervisor examples: VMware Workstation and VirtualBox.
• Type 3 hypervisors : they are called hybrid hypervisors and are those that run on the hardware but at the same time exchange information and communicate with the operating system that acts as a host. In this case some examples are: Microsoft Virtual PC, and Parallels.

You should know that the last type many experts do not consider as such and place them within the type 2 hypervisors, the hosted ones.

Advantage

The advantages of the hypervisor are several, some of the most interesting being the following:

• Thanks to the fact that on the same server you can have numerous virtual machines, we can make the most of it and ensure that it is not underused .
• In the same way, thanks to the use of hypervisors, the requirement of physical servers will be lower and with this the energy consumption will also be lower .
• From the previous points it can be deduced that hypervisors achieve significant cost reduction .
• The creation of backup copies of virtual machines and their subsequent restoration is easy and fast, so that in the event of an attack it is possible to react quickly and solve the problem in a short period of time.
• It facilitates teleworking, by being able to connect to a virtual machine from anywhere. Likewise, the support can be done remotely .
• In the event that an update has to be carried out, it allows us to carry out certain tests with which we can  safely verify whether it produces any incompatibility or not.

What problems does the hypervisor present?

Although, as we have seen, the hypervisor has some quite obvious advantages, it also has certain problems or drawbacks that we must take into account, these are the following:

• Although the investment in hardware may decrease as fewer servers are needed, the cost of the software increases , that is, of the programs necessary to control and manage the hypervisors. Obviously, every time a new server is acquired, it will be necessary to pay the corresponding licenses to be able to use these programs on the new computer.
• The use of hypervisors requires the use of computer tools of a certain complexity, which is why the need arises for system administrators to have knowledge in the use of hypervisors and otherwise provide them with adequate training.
• The performance achieved by a virtual machine is lower than the performance of a traditional one, since the hypervisor consumes certain resources by generating a communication layer between the hardware and the software.
• A server cannot have an unlimited number of virtual machines because its resources are limited. If you are not careful and install too many it can become saturated and underperform .