Understanding persistent vs. nonpersistent VDI

What is persistent VDI and how does it work?

With one-to-one persistent VDI, each persistent desktop runs from a separate disk image. The user's settings are saved and appear each time at login. These types of desktops allow for more personalization but require more storage and backup than nonpersistent desktops.

Pros: Customization and familiarity

It's easier to personalize persistent desktops because users can access their own data, shortcuts and files from the same dedicated desktop every time they log in. That level of familiarity may help users embrace VDI more easily because it provides consistency and customizations similar to a physical desktop.

Persistent VDI may also be easier for IT admins to manage because the one-to-one setup is similar to a physical desktop deployment.

Cons: Storage requirements and image management

Storage can still be a concern with persistent VDI. Individual, customized desktop images typically require more storage capacity than a pooled nonpersistent model that relies on a standardized primary image.  Persistent desktops can also require more planning for backup, patching, malware remediation and image drift because each desktop can change over time.

Some of the storage constraints that kept IT away from persistent desktops in the past have been reduced by modern storage, deduplication, profile management tools and cloud-hosted desktop options. Even so, persistent VDI usually creates more management overhead than a nonpersistent model because IT must account for the state and lifecycle of each user's desktop.

What is nonpersistent VDI and how does it work?

When users access a nonpersistent desktop, the desktop OS returns to a clean state after the session ends. At the next login, the user receives a fresh image. User data and personalization can still be managed separately through profile management, folder redirection, app layering or other tools, but the desktop itself does not remain dedicated to one user.

Pros: Image manageability, better security, less storage

Since nonpersistent desktops are built from a primary image, it's easier for administrators to patch and update the image, back it up quickly and deploy company-wide applications to all end users. Users can't alter desktop settings or install their own applications, making the image more secure.

Plus, if a nonpersistent desktop is compromised, IT can often reset the desktop to a known-good state by rebooting or redeploying the image. This can reduce malware persistence and simplify recovery. However, IT must still protect credentials, tokens, user data and connected applications through identity controls, multifactor authentication, least-privilege access and monitoring.

This setup also means there's less storage to deal with. User configuration settings and data are stored on separate hardware that's accessible remotely, such as a network share. That separates the OS from user data and allows admins to store that data on a lower-cost device.

Persistent vs. nonpersistent VDI is not just a storage decision. It is also a user experience, security, app delivery and management decision.

Cons: Less personalization and application flexibility

With nonpersistent VDI, personalization requires more planning because the desktop itself does not persist for each user. Some organizations use nonpersistent VDI specifically to reduce profile and image sprawl, while others pair nonpersistent desktops with profile management tools to preserve user settings, application preferences and data across sessions. This approach can give users a more consistent experience without requiring IT to maintain a dedicated desktop image for every user.

Since users share a common disk image, there's a certain amount of desktop customization admins need to ensure users can access all the apps they need. Virtual desktop admins can create several primary images for this situation -- one image for each type of user or department based on the users' needs.

IT administrators can also use application management, application virtualization and app layering tools to deliver applications separately from the base desktop image. This can reduce the number of golden images IT must maintain and make it easier to update, assign or remove applications based on user roles. Tools in this market include Citrix App Layering, Liquidware FlexApp, Numecent Cloudpaging, Omnissa App Volumes and others.

Lastly, it's important to note that not all apps lend themselves to being virtualized. Legacy applications, especially, may cause issues when organizations try to virtualize them.

How to choose between persistent and nonpersistent VDI

For IT leaders, the decision should start with user requirements rather than the technology model. Persistent VDI is often a better fit for users who need a highly personalized desktop, specialized applications, offline-like continuity or more control over their workspace. It can also make sense for developers, power users and employees with complex application or configuration needs.

Nonpersistent VDI is often a better fit for task workers, call center agents, shared workstations, contractors, training environments and other use cases where consistency, fast recovery and simplified image management are more important than deep personalization.

Organizations should also consider whether desktop as a service (DaaS), cloud-hosted virtual desktops or modern profile and app delivery tools change the tradeoff. In some environments, nonpersistent desktops with strong profile management and app layering can provide enough personalization while preserving the management and security benefits of a pooled model. In others, persistent desktops remain the better choice because user workflows require dedicated state and customization.

Editor's note: This article was updated to improve clarity and include current VDI decision factors around DaaS, profile management, app delivery and security.

Alyssa Provazza is the former editorial director for Informa TechTarget's Enterprise Software and Services Group.