Introduction to Server Virtualization

Server virtualization is a technique that involves the masking of server resources. This virtualization divides one large physical server into small “virtualized” servers in order to maximize the available resources.

The identity and number of individual physical servers, operating systems (OS) and processors from server users are all masked in this technique. At its simplest, the physical server is divided into virtual servers by using specially developed applications that make it easy to perform this task.

The virtual servers arrived are generally known as virtual private servers, but they may also be known as emulations, containers, instances and guests. There are many ways of server virtualization. Three of the most common ways are:

The Virtual Machine Model
This type of server virtualization is based on the guest/host paradigm. Each host or guest runs on an imitated version of the hardware layer. This approach is of great use because it allows the OS (guest) to run without the need for any modifications.

This technology also gives users the ability to create guests that can run different OS. The guest does not need the information of the host’s OS (e.g., Linux, Windows, etc.) because it does not get affected by it; The guest is not even aware that it does not run on real hardware.

However, it does need real computing resources that are provided by the host. In such a scenario a hypervisor is used to coordinate instructions to the CPU.

The hypervisor, known as a virtual machine monitor (VMM), is of strategic importance due to the critical role it plays. The VMM validates the instructions issued by the guest CPU and handles codes that require any additional privileges. This virtual machine model is used in some of the most commonly utilized servers including Microsoft Virtual Server and VMware.

The Paravritual Machine Model
The paravirtual machine (PVM) technology, like the above mentioned system, is also based on the guest/host paradigm. Additionally, it also uses a virtual machine monitor. However, the main difference is in how they function. The VMM in this scenario performs a job called porting that involves the modification of the guest OS code.

These systems are powerful enough to run multiple operating systems and the porting technique allows using privilege systems calls cautiously. Some examples include UML and Xen.

Virtualization at the Operating System Layer
This type of server virtualization is different from the two mentioned above. This is not based on the usual guest/host paradigm. In this scenario the host runs only a single operating system kernel. However, it exports OS functionality to its guests that may use the similar OS, which comes in different distributions.

This reduces CPU usage overhead by eliminating system calls between the layers. This system also requires all the partitions to stay isolated from each other so that one partition does not impact other partitions in any negative way.

In this system, virtual servers can host thousands of guests simultaneously due to the sharing of libraries and binaries on the same physical machine. Examples include Solaris Zones and Virtuozzo.

Source: GoArticles by Author Sarah Paul of US Resources, formerly called LAN Solutions Inc.; The company provides IT solutions to some of the biggest companies in the country. They are also known for their cloud-based solutions and have very broad range of IT-based services. US Resources also offers human resources solutions along with Integrated Marketing solutions. US Resources is known for handling large scale projects related to outsourcing solutions as well. Please visit them at US Resources  for more information.

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