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Centralized Desktop & Presentation Virtualization
Sudarshan Yadav
Saturday, August 1, 2009
Information Technology (IT) is one of the important functions in an organization and is a key value generator. In the current economic condition, there is more pressure than ever before on IT departments to deliver business value, despite challenges such as shrinking budgets, rapidly changing technologies and increasing security issues.

Most organizations invest into single purpose hardware resources such as rich desktops and servers, resulting in a large numbers of underutilized hardware. Additionally, managing such hardware and software takes its own toll on IT departments and impacts deployment, configuration and support. A combination of these challenges can quickly exhaust the IT department’s resources, freezing innovation and proactive planning. Studies have shown that each year IT departments spend more than 70 per cent of their budgets to maintain existing systems, leaving only 30 per cent to spend on new capabilities that add business value. The key challenge for IT is to be able to strike the right balance between managing the organization’s existing infrastructure and adding business value.

Virtualization technologies make it possible to overcome these problems by decoupling various layers of IT infrastructure. By adopting virtualization technologies, IT organizations are able to visualize each layer as a set of logical resources and deploy these resources in an agile and efficient manner. A typical deployment has application, data, operating system (OS) and hardware layers. In a traditional setup each layer is tightly integrated that makes it extremely difficult to adapt to new business needs which often require many of these layers to change. For example, if an organization needs to deploy a new LOB application which does not work on existing desktops due to higher configuration requirements or OS compatibility issues, the IT department is forced to go for desktop hardware upgrade, or rewrite the application. More often than not, these solutions are very expensive from both acquisition and maintenance perspective. Virtualization has the potential to transform the IT infrastructure by optimizing server deployments, faster application deployments, reducing downtime, risks and costs and improving the overall agility of the IT organization.

Presentation virtualization, which is one of the core virtualization technologies, makes it possible to run OS or application in one location while it can be controlled from another. Adoption of this technology unbinds the OS and application layer from the hardware layer. With presentation virtualization, OS or applications are installed and run on centralized servers in the datacenter with screen images being delivered to the users’ machines. The user’s client machine sends keystrokes and mouse movements back to the server. A good implementation of the presentation virtualization technology should provide good user experience on high latency networks and support device redirections such as printers and ports.

Below are some of the key benefits of centralizing desktop & application through presentation virtualization.

Reduced cost of ownership
When OS or application is deployed on a central server and shared among users, it drastically reduces maintenance costs.

* Ability to use thin-client in place of rich client reduces acquisition & maintenance cost. Maintenance of a thin client is less then 10% of a regular desktop.

* Less IT workforce is needed at branch offices, as the application and OS are maintained at the central data centre.

Agile application and OS deployments

*Application can be made available from server to client desktops on which the application cannot run natively. Desktop hardware upgrades are not required to deploy new applications.

*Higher flexibility to upgrade and provision OS to the users.

Improved Worker Efficiency

*Remote or mobile workers can easily connect to critical resources from branch office, home computer or airport kiosks that are not installed on the local client machine.

*Instantly Web-enables native Windows applications without costly re-coding.

Securing Data and Applications

*As applications and data reside in the datacenter, risk of data theft when a laptop is lost or stolen is eliminated.

*Adherence to regulatory compliance rules becomes easier.

The rapid development of virtualization technologies have led to the emergence of multiple options for centralized desktop and application deployments, with each having its own advantages and shortcomings. Traditional Session (terminal services) based deployment option is still the most scalable and high performance solution. The session based option is based on the capability of Windows server to create multiple sessions on single instance of OS. With this option, administrator installs and manages a complete desktop on centralized servers in the datacenter and users connect to through presentation virtualization technology. The administrator can also restrict the presentation to a specific application in place of a complete desktop. This option benefits task or office workers who require access to an entire desktop that contains few simple applications or specific applications which is not suitable for the client’s machine.

However, there are limitations with this solution. Users cannot get administrative rights to the machine as that can impact users working on other sessions on the same machines. There are also application compatibility issues due to OS compatibility with the applications and application concurrent execution.

Client VM (Virtual machine) based centralized desktop deployment is another leading option for centralized desktop deployments and is also known as VDI (virtual desktop infrastructure). In this option, client OS is hosted on servers in the datacenter and the user connects to it remotely using presentation virtualization. The user can be assigned a dedicated VM, so that all user data (such as My Documents) and profile information (personalization) are retained on the VM image. This deployment is suitable for knowledge workers (eg. software developers or testers) who require administrator rights to have full control over their virtual desktop to deploy their own applications and to customize environment.

Another deploying option is through pooled VMs that are identically configured. Pooled Virtual Desktops are best suited for office or task workers who need to work on some standard applications and do not require personalized desktop configuration or customization. In this configuration, when a user’s session ends the data is not stored on the virtual machine. A typical configuration uses folder redirection to save data to another server so it is available when the user logs in next time but no configuration data is saved between sessions. The VM based option overcomes the limitations of session based deployments of administrative rights and application compatibility but it is less efficient in terms of the number of users that can be accommodated on the server hardware. For example, session based infrastructure can accommodate almost ten times the number of users than a VM would on the same server hardware for the information worker scenario.

New developments are taking place in VDI technology, which will make the client VM image move along with the user when the user does not have access to the datacenter. This will help an IT organization to have a client VM image as per prescribed standards, while allowing employees to use their personal laptops at work and when offline. Broader hypervisor support on laptop hardware and enhancements to the VM differential disk technologies are needed for these initiatives to be successful. Similarly, in the recent times cloud based computing is also becoming popular but the current focus is on the web applications & services. At some stage desktops as a service from cloud will be a reality, but it will take several years to be viable option for centralized desktop deployment.

The multiple centralized desktop options available today make it possible for organizations to utilize their IT resources more efficiently. However, organization must evaluate the options and then decide what works best for their business needs. Centralized desktop is not suitable in all circumstances. For example, if the desktop is primarily used for high-end multimedia applications, rich desktop is still the best choice. Don’t forget, it is not “all or nothing” proposition, you can use a mix of rich and centralized desktop and bring in the benefits of both options.

Author, Sudarshan Yadav, Sr Program Manager, Remote Desktop Virtualization, Microsoft India Development Center
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