Nonpersistent vs. persistent VDI showdown
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In Robert Frost's The Road Not Taken, the poet describes the experience of choosing between two paths at a fork in the road. VDI shops face a similar dilemma between the persistent and nonpersistent desktop paths.
Persistent desktops give users their own personal desktops, similar to a physical deployment. With nonpersistent desktops, users are randomly assigned a desktop every time they log in. Many IT departments chose to use both persistent and nonpersistent desktops in a hybrid deployment, as well.
Although the choice is IT's to make, there are certain considerations to take into account, such as customization, storage and ease of management. It is an important decision for the time, money and resources a VDI deployment requires.
What is down the persistent VDI deployment path?
A persistent VDI deployment delivers a more personal touch and classic feel of a traditional desktop to users. Each desktop runs from a separate disk image, allowing users to save settings, files and shortcuts that reappear at each login. Instead of revamping its back-end infrastructure, IT can keep the 1-to-1 ratio similar to its physical desktop deployment.
IT must be vigilant in keeping track of the fluctuating numbers of persistent desktop images it has to manage, however, because persistent VDI demands a lot of storage for each user's personalized image. Storage for the disk images is typically located on a separate logical drive, then integrated back into the underlying virtual machine. The rest of the user data is stored on the virtual desktop itself.
What is down the nonpersistent VDI deployment path?
A nonpersistent VDI deployment is a fresh start each time users log into their desktops. No settings, data or files are saved. A master or golden image holds all the data in one place, making it easy for IT to manage and secure the centralized image. If IT pros want to add a new app, they can push it to all desktops by adding it to the master image. If there is a hack or compromised application, they can wipe all the desktops clean in one fell swoop.
Nonpersistent VDI often compromises user freedom in favor of tighter security and simpler management, which is the biggest drawback to this approach. Users cannot save any personal settings, including passwords, desktop backgrounds or internet favorites.
Are there ways to customize nonpersistent desktops?
Microsoft's roaming profiles store user settings on a network server, rather than on the desktop itself. Roaming profiles allow nonpersistent VDI users to attain some level of personalization. IT can configure Active Directory to connect the roaming profile with the correlating user account. When a user logs on to a nonpersistent virtual desktop, the server downloads the roaming profile to the OS in use. Any changes are then saved back to the central profile repository before the virtual desktop resets, which gives consistency to users.
Roaming profiles have been around for a long time, but the introduction of Microsoft's User Experience Virtualization (UE-V) gave the profiles new storage abilities. For example, UE-V uses XML file templates to specify the location of settings, so the server can more easily pinpoint the specific user's personal data each time he logs in.
The problem with roaming profiles is it brings back the issue of storage that nonpersistent desktops aim to solve. Roaming profiles can grow too large, because each time users log on and off, the profile has to transfer and save the data. The login times get longer, as the roaming profiles weigh down desktop resources.
IT pros can also layer virtual disks and include a user profile layer. The lowest layer is the desktop OS, and the next layer is typically applications for all users. IT can add any additional layers it needs to allow for restricted access to certain applications. The top layer is for user personalization, which saves any changes users make to individualize their desktops. IT can split this layer into two for applications and custom settings.
How to choose one path -- or both
IT pros who find themselves split over which VDI deployment approach to choose must consider their employees first. For workers who are simply entering data or performing basic tasks, nonpersistent VDI can give more pricing flexibility, because the hardware required to run these lightweight desktops is often simpler and less expensive. A worker who is dependent on saved files, shortcuts or applications may benefit from persistent VDI.
Lastly, the choice is not as black and white as Frost puts it in his poem. One organization may want to deploy both nonpersistent and persistent desktops. Perhaps one location, department or branch office is better suited for persistent VDI, and the others are not. The combination can get tricky, costly and requires close IT management, but combining both options can provide just the right mix for some businesses.
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