Desktop as a service vs. VDI: What's the difference? How to calculate VDI costs and keep them to a minimum

3 VDI challenges that can derail any project

IT shops need to look out for complexity, cost and performance problems when they put a VDI implementation plan in place.

Few technology-based projects are as simple to build and maintain as vendors suggest, and VDI takes that to a whole new level.

The promises of cost savings and lower administrative overhead can quickly evaporate in the face of VDI challenges. Because of cost, complexity and performance problems, many organizations scale back their VDI projects or abandon them altogether.

Unexpected complexity

One of the fundamental promises of VDI is simplified desktop management. Rather than having to deal with multiple independent physical desktops, administrators can centrally manage relatively few desktop images, making it simple to perform such tasks as updating software or applying security patches.

VDI management includes a lot more than just maintaining desktop images. Administrators must tend to the servers, hypervisors, storage systems, networks, software and more. And they must still contend with the physical client systems. Admins even have to manage thin clients and mobile devices.

VDI administrators require a different skill set to keep the various pieces running and deliver quality performance and reliability. They must carefully balance and control the ports, subnets, protocols and VLANs that support virtual desktops. Many also have to deal with application layering, which is intended to reduce the number of base images, but actually increases overall complexity. In addition, VDI requires fault tolerant systems to avoid any single points of failure in the server, storage and network infrastructures.

One mistake can take down hundreds or thousands of virtual desktops in a single blow.

Administrators must contend with issues that arise when virtualizing certain types of software. The big-name players, such as Microsoft Office, work in the virtualized world, but legacy and specialty apps often require hand holding to meet the demands of virtual desktops.

Security requires special attention as well. Although VDI can make it easier to centrally manage and protect data, one of its selling points is that it allows users to remotely access their desktops from different locations and devices. This makes it more complicated to protect the network and its underlying systems because it increases the attack surface area. Running antivirus software is more of a challenge because of the load it puts on systems if the software scans too many virtual desktops simultaneously.

To make matters worse, the stakes are often higher with VDI because one mistake can take down hundreds or thousands of virtual desktops in a single blow. Therefore, it's even more important for VDI admins to implement a solid business continuity plan to protect critical infrastructure and achieve high availability.

Poor performance

Nothing kills a VDI project like a few hundred disgruntled workers. For end users and admins, poor VDI performance is public enemy number one. Although VDI has come a long way in addressing performance issues, problems still remain, and solving them can be costly.

The main culprit is usually storage infrastructure. To realize VDI savings, IT teams often try to load as many virtual desktops in the least amount of storage space possible, resulting in input/output latency and contention issues.

The typical VDI storage system must be able to handle morning Boot storms, antivirus scans, software updates, system backups and unpredictable user workflows.

Higher storage densities can also require increased power and cooling resources and can strain the network when it tries to handle the traffic filtering in and out of the storage system. If an organization consolidates its data centers into a few regional locations, users are likely to experience even greater latency, depending on proximity.

VDI can also strain network resources, because all the desktop data travels back and forth between the data center and the client. To complicate matters, many organizations work with network infrastructures that were in place before VDI existed. Administrators can augment those networks, but the basic architecture was still conceived without VDI in mind. Other hardware components can also lead to poor performance, such as having servers in place that cannot meet processing demands.

Network latency can significantly deter user experience as well. It can make multimedia apps almost unusable, especially when supersized files are involved. To address these issues, vendors use complex workarounds, such as bypassing the remote protocol when directing the video stream to the client. Unfortunately this means running the video player on the client, which undercuts the benefits of desktop virtualization.

Unanticipated costs

The resources VDI shops need to maintain the appropriate levels of performance and redundancies to keep workers productive aren't cheap. Consider that all the desktop data must travel over the networks and be stored in centralized data centers, with back-end servers doing the grunt work. An organization must invest in the hardware necessary to implement such an infrastructure, which includes redundant components and periodic replacements to keep everything running.

When looking into VDI, decision-makers cannot allow themselves to focus only on the amount of money they can save through the promise of thin client computing. Getting VDI going can represent a significant investment on its own, because it often means adding to or replacing existing hardware. Having to then invest in additional hardware, and resources to put that hardware in place, quickly tarnishes the cost-saving glitter of VDI.

As a result, VDI shops must constantly strive to balance costs against performance, which often leads to a greater capital outlay than they originally estimated. Hyper-converged infrastructure can sometimes lower the costs of VDI by using resources more efficiently, however.

Organizations must also tread carefully when it comes to licensing software. Windows and application licensing with virtualization can be confusing and complex. If an IT team doesn't get it right, it can end up the victim of a vendor audit that results in substantial fines.

Before an organization makes an investment, it should carefully evaluate the optimal use cases for desktop virtualization. An organization with local and remote knowledge workers, for example, would be a good fit for VDI. For an organization that heavily employs mobile task workers, on the other hand, the cost of VDI would outweigh the benefits. A proof of concept can help organizations determine whether VDI is the right choice.

Organizations must also take into account the cost of the IT personnel they need to implement VDI, maintain the software and hardware, and support users. To get the infrastructure up and running, an IT team might need to bring in special consultants or pay VDI vendors for premium support.

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