The Operating System Virtualisation Computer Science Essay

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OS virtualization is a technique which provides many benefits such as costs and a more effective way of utilizing resources. It provides a more secure and efficient way of providing clients access without compromising security, efficiency and usability. This document describes the basic principles of OS Virtualization along with its pros and cons, suitable scenarios in which it is used, available OS virtualization software and its current status and predictions of it's future.

In todays technological age the number of computers is increasing being non work places, corporate environments and government departments is increasing rapidly. This continues to be true as computers get cheaper and continue to be upgraded resulting in technological cycle that continues to thrive in today's market. However as the purchasing and use of computers continues to grow so does the underlying issues such as management problems and security issues. These issues can be a constant problem especially for those working in corporate and government departments where there is a large scale of computers. However this is where OS Virtualization comes into play and can these key issues. OS Virtualization is a technique that was introduced by the Ardence Company and is a technique that continues to grow in popularity to this day.

OS Virtualization what is it?

OS virtualization is a technique is used when resources e.g. hardware is limited requires virtualization so that the physical requirements are kept to a minimum. Instead of using a physical hard drive it connects to a network which utilizes a virtual disk which contains the pre loaded or pre installed operating system. This allows multiple users to use the same computer with their desired settings and access instead of one user per desktop computer. This reduces security risks because there is no hard disk and because users can be placed into different containers which can give them access to areas they only require. This is where virtual disks come into play.

Virtual Disks

Virtual disks are not only made for operating systems but can be utilized for application use as well. The client software is installed on this system and allows them to connect to the network. Virtual disks are created using a special imaging technique. In typical implementations of os virtualization there are two types of virtual disks.

One of them is the Private Virtual Disk in which a single user/client can make changes to the information that is stored on the disk. This is similar to a normal desktop in the way that all the changes that have been made are still contained even when the user logs off.


A shared virtual disk (sometimes referred to as a common virtual disk) in most cases is used by a number of clients at the same time. Each user is given a unique identifier and when logged in any changes made are stored in a special cache. However unlike Virtual disk the client's configurations are wiped off whenever they restart or shutdown and when re booted load the default configuration stored on the virtual disk.

OS virtualization and how it works

The server is the most important element of the OS virtualization. This is because the server is the one that provides information from the virtual disks needed by the client by utilizing a technique called streaming. While streaming this information the server also makes sure the client is connected to the right place e.g. Private disk or shared/common disk. The server also makes sure that each client has a unique identifier. The server can store data in itself or use other storage technologies such as a SAN (storage area network) or NAS (Network attached storage).

Subsequently the operating system can be run from a virtual disk when the client requests it. The elements that support this can be TFTP or PXE which provide streaming and allow one to load content stored on a disk.

The client will ask the virtual disk to boot the system and verify whether will be allowed to access and authorization to do as he/she pleases.

The virtual disk contains an image that saves all the configurations and those particular configurations are saved by the server. The administrator than makes sure the connection is made and monitors these changes that have been made and that have been stored onto the database.

OS Virtualization: The Pros & cons

There are plenty of pros and cons when it comes to OS Virtualization the ones stated below are just a few of them.


Provides Flexibility

In comparison to traditional methods it is relatively easy connect to a virtual disk, switch/mage client roles and switch operating systems with OS virtualization. Terminal environments in particular will find the usefulness of flexible provisioning.

Multiple images across many systems

Multiple services can be provided to a particular client this could mean a certain user could choose which operating system they would want to use. This is done by providing a number of images to a client at the same time. This improves felexibility and allows the system to be used for a number of reasons.


Rapid software/application deployment

Rather using old deployment methods such as manually installing and configurations which can take a long time, OS virtualization provides an alternative to deploy operating systems and application software in a much faster and more effective way.


If a system is not working properly and a quick fix is not at hand a virtual disk that has stored a previous state can be used. This makes it easier to roll back the system to when it was working properly. This option is much better than the traditional methods of rolling back which could often cause more issues than resolve them.

A clean slate

When systems are rebooted they are restored to a clean slate unlike a traditional system that is not working properly, OS virtualization eliminates the need of manually reinstalling a system by simply resetting the system. This in turn restores the default settings but this is only applicable to shared images.


Offline is not an option

OS virtualization requires a connection to a server which means that staying online is a must in order for the client to access the operating system on the virtual disk. Because the client must connect to a server it is impossible to access the virtual disk without online access.

High speed Lan is a must

In order to run at a smooth rate a broadband connection at least 100mb or greater is recommended. Otherwise the system will become slow and congested due to the lack of bandwidth available. Wide area networks are also difficult to run at a smooth pace.

Operating system compatibility

Although there are a number of operating systems that are currently work with OS Virtualization there are still some lack support. The operating systems primarily consist of Linux although even some Linux operating systems do not work.

Imaging issues

All issues that apply to imaging are applicable to os virtualization. This can be problematic because imaging techniques are used to create the virtual disks that are used in os virtualization.


Possible Scenarios in which OS virtualization can be used

Terminal Server

The terminal server and os virtualization go well hand in hand because the terminal server will keep the default changes even when the changes have been applied to the virtual disks.

Back up servers

Back up servers can be utilized to their full potential by using flexible provisioning instead of being unused for the most part. Backups can be stored on another virtual disk which then can be used by the back up server.

Web servers

Data can be stored on a local server instead of typical web servers which are generally static cannot save data locally. The server which is used by os virtualization can utilize a virtual disk which contains a backup.

Education environment

It can be very difficult maintaining a large amount of students along with a fully functioning and non-problematic system. Also catering to different students by providing them different environment's ad operating can be solved by OS virtualization. OS virtualization allows a variety of things that cater to the client's e.g. operating system and also resets any changes made after rebooting.

Lab environment

Students need to be able to do labs on the go and with OS virtualization restores the system to the default state allowing them performs labs successfully. Flexible provisioning also helps with providing the environment which is suitable for the environment.

Public workstations

OS virtualization is suitable for these kinds of environments because anyone can access them. Any sensitive data such as personal information that has been entered by the client should not be kept and erased off the system to ensure that there are no security issues.

Current developments

In the os virtualization market there are two main players they are Citrix and Xtreaming. The main systems are currently run using citrix and are used in a variety of environments and different situations. The ones that are utilizing citrix products use software such as Citrex Xendesktop which is used to implement VDI's.



In todays the market the desire for virtualization continues to grow to this day. Although physical computers improve and become cheaper the virtualized equivalent also continues to grow. OS virtualization provides a cheaper and secure alternative with virtual disks (in comparison to physical disks) and is more versatile by providing flexible provisioning. It can be used in a variety of environments such as terminal servers, web servers, public workstations, education and lab environments etc.

However for all the benefits there is in OS virtualization it does have its shortcomings. It requires a good broadband connection and operating system support is currently limited. Also online access is a must otherwise a client cannot retrieve data that it requires from the virtual disk in the server. However with all technology it is ultimately up to those in charger an dos virtualization does provide a good alternative and will become a more viable option once the issues that have been shown in this report are eliminated or minimized.