Persistent or Non-Persistent VDI?

The fundamental objective when implementing virtual desktop infrastructure (VDI) is to ensure that the end user experience is at a minimum, equivalent to the same experience as a physical desktop. Poor performance and the lack of desktop customization is a formula for creating end user dissatisfaction and ensuring the rejection of a VDI project. The question is, what is the best way to satisfy end user demands while capturing the same business benefits that have been realized through server virtualization?

There are two methodologies for deploying VDI – persistent desktops and non-persistent desktops. Some industry observers believe that on paper, non-persistent desktops offer more tangible business benefits than persistent desktop systems. They claim, however, that persistent desktops are the only viable method for deploying VDI. Let’s examine the case for each.

The Allure of Non-persistent VDI

For starters, all the required resources to power a virtual desktop (CPU, RAM and storage) can be fully virtualized and shared on an ‘on-demand’ basis across hundreds or even thousands of users. This enables infrastructure planners to do more with less as many environments rarely, if ever, have to support 100% of their end users at any given point-in-time. A certain number of non-persistent desktops can also be pre-allocated to give designated users a “quick-on” experience.

Another advantage in non-persistent VDI deployments is that a single operating system and application image on a hypervisor server can service hundreds if not thousands of VDI users. This makes system maintenance and application upgrades significantly easier to manage. On the downside, non-persistent environments do not maintain user profile settings, wallpaper and other customized configurations. Instead, a generic desktop configuration is presented each time the user logs in to their virtual desktop.

The Persistent VDI Comfort Factor

The principal rationale for deploying persistent desktops, on the other hand, is that it seems to be the best way to guarantee an end user experience that most closely emulates a physical desktop. Like physical desktops, persistent desktops allocate storage, CPU and RAM resources to each virtual desktop.

Another attribute of persistent desktops that is similar to a physical desktop experience is that end user customization settings can be maintained. This means that each time an end user logs in they will get the same desktop “look and feel”, regardless of the physical location that they sign in from. Advocates of persistent desktops also point out that existing physical desktop maintenance tools can be utilized to manage application upgrades, etc. making it easier from an operational standpoint to make the shift over from physical to virtual desktops because there are no new tools to learn.

The Challenges of Persistent Desktops

One of the challenges, however, with persistent desktop environments is that physical storage, CPU and RAM resources are essentially hard allocated to each and every user; regardless of whether or not they are actively logged in. For large VDI implementations, this can drive up costs dramatically.

Additionally, since each persistent desktop maintains a unique operating system image, system maintenance and data protection becomes a much more challenging task. In a 10,000 seat persistent desktop VDI implementation, for example, unless advanced storage systems with deduplication are used,10,000 unique system images need to be stored on disk and backed up regularly to ensure that user customized settings will not be lost.

What’s more, legacy desktop maintenance tools don’t do anything to mitigate the risk of a severe VDI service disruption resulting from general maintenance activities, like a simple application upgrade. Pushing out an Adobe or Microsoft Office application upgrade across hundreds of persistent desktops, could bring even the most advanced VDI host cluster and shared storage system to its knees. Consequently, persistent desktop administrators have to carefully orchestrate these types of maintenance activities to minimize any impact to their end users; adding complexity to the management of the environment.

The Best of Both Worlds – Software Enhanced Non-Persistent Desktops

Fortunately there are now VDI software tools available, like those from Liquidware Labs, which enable businesses to get the best of both worlds. These tools enable businesses to exploit the resource efficiencies of non-persistent desktop environments while enabling user desktop customization and ensuring consistent virtual desktop quality of service (QoS). They include capabilities that manage profiles and accelerate storage performance.

In many environments, non-persistent desktops can well serve the majority of end users that need access to common applications, while a select few “power users” may need the raw horsepower and performance that persistent desktops can deliver. The point is that it is no longer an “either/or” proposition now that mature VDI software tools are available.

The Storage Challenges of Persistent and Non-Persistent Desktops

Part of the decision making process for Persistent and Non-Persistent VDI has to do with how that choice will impact storage. For an in-depth look at how to overcome the storage challenges in persistent and non-persistent desktop environments, please register for our white paper, “The Storage Impact of Persistent and Non-Persistent Desktops”.

Liquidware Labs is a client of Storage Switzerland

As a 22 year IT veteran, Colm has worked in a variety of capacities ranging from technical support of critical OLTP environments to consultative sales and marketing for system integrators and manufacturers. His focus in the enterprise storage, backup and disaster recovery solutions space extends from mainframe and distributed computing environments across a wide range of industries.

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