Virtual desktops: Use client-side or server-side hypervisors?

With so much progress made virtualizing servers, many observers say it's time to turn our attention to the desktop. But is it better to use client-side or server-side hypervisors?

The Experts
Purnima Padmanabhan
Purnima Padmanabhan

vice president of products at MokaFive says client-side is the way to go because you need to be able to carry the “desktop” around with you on different devices. View debate

Margaret Lewis
Margaret Lewis

Director of Commercial Software Solutions at AMD argues that the client-side approach isn’t fully baked, while the server-side tools are mature, trusted, and already delivering key benefits. View debate

Purnima Padmanabhan

Client-side hypervisors

Hypervisors have, at long last, allowed us to detach the desktop from the device, opening up tantalizing possibilities. But while many vendors are pushing server-side hypervisors, where desktops are hosted on a server hypervisor in a data center, key trends indicate client-side hypervisors are the way to go.

Client-side hypervisors encapsulate all software of a desktop -- OS, applications and data -- into a virtual machine, and allow it to be run locally on any computer, be it Mac, Windows or Linux. And, since the client-side hypervisor is run directly on users' computers and not in a far-off data center, it is always available, whether online or offline.

Hypervisors have thrown the neat notion of a monolithic physical desktop into flux. But where are we headed? To better understand this, three important developments need to be considered:
• The arrival of super devices. Personal devices are mobile, ever-more powerful, capacious, and incredibly affordable. Laptops with 4GB of RAM and 320GB of storage are now less than $500. Increasingly users will expect to use their personal devices for both work and play.
• The rise of the cloud app. Over the last few years Google search, Facebook and Salesforce have defined a new class of application that runs in the cloud. Users will need to access these cloud apps while also being able to use rich local applications like PowerPoint.
• Hot spots, cold spots. Network coverage has grown, but is far from ubiquitous, especially in areas of low population. Therefore, for the mobile professional, offline desktop access will continue to be mandatory.

Peering ahead five years, the future desktop will be independent of the device and users will always have it with them anywhere, anytime and on any of their super devices. The "desktop" will let users access cloud apps and also use rich local apps, whether online or offline, hot spot or not. It also will be resilient, automatically recovering from failures. And the best part is that it will be managed and secured by a provider: be it your IT department, your ISP, or even your phone company.

This future desktop can only be achieved by a client-side hypervisor. In this approach, your desktop provider defines and secures the virtual desktop image in the cloud. Users download the image to any device and run it on a client hypervisor locally, online or offline. Any work done in the image is kept separate from the personal host OS. If the virtual machine gets infected or damaged, it can be recovered by users themselves, even if they're offline.

Server-side hypervisors won't cut it. Here's why.

First, scalability. With client-side hypervisors, new users can be added with little impact. By contrast, the server-side approach comes with specific capacity limits and requires you to overbuild for peak capacity.

Second, reliability. A decentralized system is inherently more resilient than a centralized one. With client-side hypervisors, a failure may bring down one user, while with server-side hypervisors, a single incident can bring down the entire company.

Third, security. Unlike a server-side approach which only secures the data in the data center but is vulnerable when accessed from an unmanaged machine, client-side hypervisors provide a secure container on the device, protecting user and company data.

Fourth, cost. Client-side hypervisors are elegantly simple and, because they use commodity CPU and storage, are low cost. The server-side approach is bewilderingly complex and requires expensive servers, network upgrades, and SAN storage.

Finally, responsiveness. With a client-side hypervisor, users can access their cloud apps as well as rich interactive apps, such as Microsoft Office. The server-side approach, by contrast, transmits every keystroke and mouse click between the data center and the user, degrading the responsiveness and interactivity.

Though its proponents may say otherwise, a server-side approach offers neither the performance you need for rich, local apps, nor the simplicity of a true cloud app. In five years, when apps that need to run in the cloud are in fact purpose-built for the cloud, server-based desktops will be used only for very niche situations.

The rise in personal devices and cloud apps, and the reality of network conditions, are influencing the future desktop. And the future for desktops, contrary to the hype, will include very little of the server-side approach. Instead, the future desktop will be based on a client-side hypervisor, running both cloud apps as well as local productivity apps. And, when it arrives, it will make both users and administrators very satisfied.

MokaFive has developed a breakthrough desktop management solution that leverages the latest advances in computing technology to fundamentally change the way enterprises control and manage mobile endpoints to achieve cost reduction, risk mitigation and business alignment.

Margaret Lewis

Look no further than the server

I predicted last December that client virtualization, the decoupling of the desktop from its underlying hardware, would hit a tipping point in 2010 and begin to impact both businesses and consumers. I'd say we're gradually seeing this come true, but the question remains: What is the best approach to deploying virtual desktops?

The client hypervisor is a technology still in its infancy with virtualization leaders such as Citrix and VMware trying to push bare-metal hypervisors beyond the conceptual phase and into production. I'd argue that server-hosted desktop virtualization is the way to go today. From both a manageability and maturity perspective, virtualizing the client onto the server is a trusted technology with a proven track record.

Server-hosted desktop virtualization aims to make the user's experience seamless by offering a functional desktop system that runs as if the user had a regular PC, minus the hassles associated with actually having a fully-loaded machine on their desk. Keeping that in mind, the more invisible the solution is to the user, the better. And the less often IT has to physically wrangle with a desktop, the happier they are.

There's nothing like firsthand experience, and here at AMD we've found that server-based virtual desktop infrastructure (VDI) has performed extraordinarily well at our Sunnyvale, Calif., campus (check out this case study here). Given the choice between server-side and client-side tools, AMD opted for the server route, and currently uses VDI to deploy desktops to about 100 engineers at our development center.

There are two main types of server side VDI tools to explore.

One approach involves using a server hypervisor, like Windows Hyper-V or VMware, to encapsulate, deliver and maintain individualized desktops on a single, centrally located computer. The individual desktops are accessed via remote client devices. The goal is to offer a near-native experience without needing a fully loaded machine on each desk. Sounds a lot like cloud computing, doesn't it?

Another scenario delivers session-based desktops or applications, allowing for high user density with a limited degree of personalization or isolation. Now known as remote desktop services, the graphical user interface (GUI) is delivered to the desktop via Remote Display Protocol (RDP), which has important benefits for management and security issues. By centralizing apps and data, the server sends only as much of the OS or app as the user needs.

Regardless of which route you go down, managing desktops from a central data center is more efficient and secure than managing a dispersed set of physical computers with their related applications and data. At AMD, we have been enhancing our on-chip virtualization capabilities with AMD-V virtualization technology, as well as further increasing the memory resources and core count in our AMD Opteron 6000 Series processor to enable the robust server environment needed to efficiently drive multiple client sessions.

What's more, upgrades, license and patch management and general desktop maintenance are easier, and there's rarely a need to send someone on-site to address issues. There's also something to be said for the flexibility that desktop virtualization enables for employees.


But do client-side hypervisor solutions offer these and other benefits? A recent Network World article points out that client hypervisors can potentially deliver better performance than server-side approaches that require apps to run on remote devices. And running desktops in VMs on the client could fuel adoption of "bring your own PC" programs because a secure business application environment could be maintained within the employee's laptop.

While this scenario sounds ideal, we should also look at it from a maturity perspective. The industry is strides ahead when it comes to server-side hypervisors vs. client-side. Microsoft first introduced Terminal Services in Windows NT 4.0, providing the basic technology for users to remote access server-based applications. Today Microsoft works closely with Citrix to mature this technology. About two and a half years ago, VMware made its first foray into the server-side desktop virtualization (VDI) market with the launch of VMware VDM 2.0 (now known as Vmware View).

Compare this to where we stand with client-side hypervisors. While VMware is arguably a leader in server side VDI, it has yet to roll out a Type 1 (or bare-metal) client side hypervisor – otherwise known as a bare-metal desktop hypervisor. Citrix has just barely entered the market with a client side desktop virtualization tool, rolling out XenClient in May of 2010.

Server-side VDI solutions have been on the market for several years, offering providers ample time to test and refine performance with real world case studies guiding the way. With only four months of availability under its belt, client-side tools like XenClient are still earning their stripes. That is not to say that client side solutions won't play an important role in the future. However, server-side tools are the best option for businesses who want an effective, proven desktop virtualization solution today.

Advanced Micro Devices is an innovative technology company dedicated to collaborating with customers and technology partners to ignite the next generation of computing and graphics solutions at work, home and play.

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