Demystifying desktop virtualization technology
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When it comes to virtual desktop infrastructure, administrators have a lot of choices. You may have wondered about the differences between VDI software options, remote display protocols or all the licenses out there. In this series, we tackle some of the biggest head-scratchers facing VDI admins to help you get things straight.
There are two main types of desktops you can deploy in a virtual desktop infrastructure (VDI): persistent and nonpersistent. So what's the difference?
With persistent VDI, each user gets his or her own desktop -- also known as a one-to-one ratio. Nonpersistent desktops are many-to-one, meaning that they are shared among end users. Each setup has its advantages and disadvantages when it comes to storage, management and customization, so you need to know how each environment works. Let's get this straight.
With one-to-one persistent VDI, each 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 they 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 desktop every time they log in. That aspect of persistent desktops tends to help users embrace VDI more easily.
Plus, persistent VDI is basically the same setup you had with your physical desktops, making it easier for many admins to manage. Rather than re-engineering your desktops when you move to VDI, you can stick with a one-to-one setup.
Cons: Storage requirements and image management
Storage is a major concern with persistent VDI. All those individual, customized disk images require more storage capacity than a single golden image does with nonpersistent desktops. Storage for persistent desktops is usually a separate logical drive, so it's integrated with the underlying virtual machine, while the actual user data is stored on the desktop itself. Recently, more storage products and features have been made available for persistent desktops, eliminating some of the storage constraints that kept administrators away from persistent VDI in the past.
An additional concern is that it's more complex to manage numerous diverse images than a master image that can be altered and updated in one stroke.
Series: Let's get this straight
Comparing thin clients to fat and zero clients
Comparing remote display protocols
Application virtualization smackdown
Clearing up Microsoft VDI licensing: SA vs. VDA vs. CDL
How cloud-hosted desktops differ: Comparing VDI, DaaS
When users access a nonpersistent desktop, none of their settings or data is saved once they log out. At the end of a session, the desktop reverts back to its original state and the user receives a fresh image the next time he logs in.
Pros: Image manageability, greater security, less storage
Since nonpersistent desktops are built from a master 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 the image is hacked or compromised, you can simply reboot desktops back to a clean state.
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.
Cons: Less personalization, application flexibility
With nonpersistent VDI, users cannot easily personalize their desktop. That's because nonpersistent desktops don't require individual user profiles; in fact, some organizations deploy nonpersistent VDI so that they don't have to manage profiles. You can even configure user profiles to delete themselves automatically from desktops using VMware View or Citrix XenDesktop pools.
Since users share a common disk image, there's a certain amount of desktop customization admins need to do so that users can access all the apps they need. That often requires application virtualization or user environment virtualization, which can get complicated. Plus, not all apps lend themselves to being virtualized.