Moving Forward with Client Virtualization

by Joe Chow




Virtualization in computing, according to Wikipedia, “is the creation of a virtual (rather than actual) version of something, such as a hardware platform, operating system, a storage device or network resources”. The same virtualization concept can also be extended to include virtualization management, virtualization of application software, and service virtualization. Readers interested in understanding various forms of virtualization can refer to documents listed at the end of this article.

Why virtualization?

Virtualization can be viewed as part of an overall trend in enterprise IT that includes autonomic utility computing, a scenario in which the IT environment will be able to manage itself based on perceived activity, and in which the total required computing resources provided, like a utility, can be dynamically adjusted according to demands so that clients are only charged for what they actually use. The goals of virtualization are to centralize administrative tasks while improving scalability and overall hardware-resource utilization to achieve reduced complexity of IT environment, simplifying disaster recovery within the data centre environment, speedy allocation/relocation of computing resources and, as a result, reduction in total cost of ownership and shortening the time-to-market (i.e. service delivery time).

Client Virtualization

One form of virtualization, virtual desktop infrastructure (VDI), can be thought of as a more advanced form of hardware virtualization. Instead of directly interacting with a host computer via a keyboard, mouse and monitor connected to it, the user interacts with the host computer over a network connection (such as a LAN, Wireless LAN or even the Internet) using another desktop computer or a mobile device. In addition, the host computer in this scenario becomes a server computer capable of hosting multiple virtual machines simultaneously for multiple users.

Client virtualization is sometimes known as desktop virtualization since it virtualizes desktop computers or personal computers (or clients). Unlike server virtualization, which is to reduce the number of physical devices in the data center, client virtualization is not used to cut the number of personal computers (PCs). Instead, it allows the administrator to turn a large number of client devices into an easy and manageable server’s administration task.

Depending on the way a virtual image interacts with the client device, client virtualization exists in several forms. Below are the two common forms.

Hosted virtual desktop infrastructure (VDI): Entire computer environment including applications, data, user settings, etc. runs on server-based virtual machines, with only screen images, mouse clicks and keystrokes transmitted between the hosted virtual machine and the client device.

Streamed virtual hosted desktop (VHD): Complete virtual machine images are created, maintained and updated in servers residing in the data centre, but they stream to individual clients for local execution. IT administrators can create a single desktop image and stream it to a number of client computers.

For the VDI solution, the client image is stored and run on the server side. The performance of this virtualization is less client dependent and can delay the requirement for desktop hardware upgrade but it requires powerful servers. Although the VDI solution enjoys the advantage of lower client’s cost , this kind of virtualization does have other limitations. Even with the most advanced server and network equipment, all VDI solutions have a problem of running large local files. In the case of playing a video file from a local DVD player under VDI, it often results in a glittered display. The problem is because, under the VDI, the execution of the local file requires the file to be sent to the server first and executed there. Execution with large local files relies on a large network bandwidth and sufficient server’s resources (CPU, memory…etc) that may not always be available through a share-based environment.

The VHD solution does not require as much server capacity as the VDI, however, it is more reliant on the network performance since the client image has to be streamed to the clients. For a class with 30 PCs running VHD, all 30 PCs have to get the images streamed to them at the same time. On the other hand, VHD has the benefit of better USB device detection and can execute large local files more efficiently than VDI since the images are basically running native at the client side.

Therefore, we cannot say which approach is more superior. People will adopt different approaches under different situations and for different client environments.

Benefits from using client virtualization

Client virtualization enhances security and improves the availability and disaster readiness because it allows IT administrators to focus on managing client images on servers located in the central data centre rather than maintaining a large number of devices scattered in different places. What is more, client virtualization offers a highly scalable solution that enables an enterprise to be more flexible when rolling out new applications and services.

How can client virtualization simplify management, improve security, reduce costs and make IT more responsive to an organization’s needs? Here are some of the benefits that companies would expect to see after implementing client virtualization technologies.

Patch Management: With client virtualization, a centralized image can be used to replicate a large number of virtualized PCs, which makes system and application patching job a much easier and more predictable task and enables rolling out of patches to all clients in a matter of simple centralized operations.

Security: Today, companies are paying more and more money to save guard from any security threats. Users may save company data on their notebooks or unsecured flash drives. Without encryption, any of this data could easily be extracted by others. With client virtualization, desktops and applications can be centralized and pre-configured in the data center. Therefore, better controls can be applied to what end users have access to.

Software Distribution Management: Rolling out software applications requires a great deal of testing work. Many new versions of software may conflict with certain versions of operating systems or other application software. With client virtualization, software distribution becomes simple because it allows IT administrators to test the applications within the data center and roll back the software installation in a matter of minutes. Taking this advantage, the time leading to roll out a new version of software will be reduced and many application compatibility issues can be mitigated before launching out the software.

Help Desk Management: Physically sending supporting staff to user’s office to repair or update devices is a time-consuming and non-cost-effective task especially if there are remote offices all over different locations. With client virtualization, system delivered can rollback instantly without going to the user’s office and this saves the help desk loading and renders the support quicker and simpler.

Concerns and risk of using client virtualization

Apart from the above benefits, implementing client virtualization has its concerns and risks to face. Many companies with successful server virtualization believe that they can do the same with client virtualization, but this assumption can cause them to fail right from the very start. Investigating all the possible concerns and risks to the company prior to implementation is important and crucial.

Concern: When deploying a client virtualization solution, one has to be sure that the overall IT infrastructure is up to the level required, especially in the areas of networking and storage. Failing to understand this will not only make the virtualization deployment unsuccessful, but also affect other services provided by the company’s infrastructure.

Concern: Negotiating with users and managing their expectations is critical but balancing the corporate culture is equally critical to a successful deployment of client virtualization. Users are accustomed to a rich desktop experience and inevitably they would expect the same experience on a virtual machine as that on a real PC. Obviously, this needs a compromise. For instance, the ability to stream high quality video cannot be provided without the use of different client virtualization technologies - hosted virtual desktop infrastructure (VDI) and streamed virtual hosted desktop (VHD).

Risk: One of the drawbacks of client virtualization lies in the word “centralization”. When everything is centralized, what happens when the entire system fails? If a company believes that client virtualization is simply running PCs inside a data centre and missing out the importance of backup and redundancy, the consequences could be drastic!