The Great Debate: Persistent vs. Non-Persistent Virtual Desktops

Transcription

1 The Great Debate: Persistent vs. Non-Persistent Virtual Desktops Persistent desktops that sustain all user and IT customizations? Or non-persistent desktops that revert back to a pristine state after each use? This has been one of the great debates in Virtual Desktop Infrastructure (VDI). Is it even relevant anymore? Find out in this white paper.

2 Introduction The debate between persistent and non-persistent virtual desktops has been hotly contested ever since Virtual Desktop Infrastructure (VDI) became a viable alternative to physical PCs. This white paper takes a look at the history and evolution of the VDI market to understand why persistent and non-persistent desktop models exist. First, we will define each model, explain the use cases, and discuss the technologies available to implement both desktop types. Then, we will debunk some of the common myths and misconceptions, and outline the pros and cons of each model. Throughout, you will benefit from actionable insights that can be used when architecting your VDI environment, and learn from the real-life customer examples that have been included for reference.

3 Evolution of Persistent and Non-Persistent Desktops To understand why there are even two different types of virtual desktop models, it is important to understand how the VDI market and the technology have evolved over time. The Persistent Desktop Era Early adopters of VDI chose to virtualize desktops primarily for the security, mobility, and anytime/anywhere access benefits. The easiest and fastest way to realize these benefits was to simply move PCs from the edge into the data center. The first virtual desktops, then, were full clones full-sized virtual machine (VM) copies of physical desktops. These full clones were assigned at login to specific users. Every time users would login, they would access the same VMs. Full clones were also persistent every change made to desktops by an end user or an IT administrator was saved. Full clone desktops were managed exactly the same as physical PCs using manual methods, or agent-based PC lifecycle management software such as Microsoft System Center Configuration Manager (SCCM), Norton Ghost, KACE, LANdesk, Big Fix, etc. Full-sized, thick-provisioned VMs proved to be quick to implement. However, they had two significant problems that limited broad VDI adoption: 1. Management. The management challenges associated with physical PCs still remained. Like physical PCs, persistent desktops would deteriorate over time, as IT and end users both made changes to the C: drive and Windows registry. As desktops deviated from each other, Windows and application updates wouldn t always take, resulting in the same 5-15% patch failure rate and costly service desk escalations as PCs. Provisioning new desktops and delivering new applications was only marginally better than PCs. 2. Storage. Persistent desktops made VDI unaffordable to the mass market due to the high cost of shared storage. The 40 GB local disk drive in a PC is cheap. That same 40 GB desktop hosted on SAN storage in the datacenter is expensive roughly 10X the cost of PC storage. Because of these issues, only organizations with large IT staffs and large budgets (e.g. Wall Street financial firms) were able to deploy persistent VDI at any scale. The Non-Persistent Desktop Era In an attempt to solve the storage and management challenges, Citrix and VMware introduced the concept of non-persistent, floating desktops. With this model, virtual desktops would reside in pools. When a user needed to access a desktop, a VM would be pulled out of the pool

4 and assigned to the user. When the user was finished using the desktop, it would be returned to the pool and all changes made by the user would be thrown away hence the term nonpersistent desktop. It was hoped that this model would address the two challenges of persistent desktops: 1. Management. By resetting desktops back to their pristine state after each use and using shared image technology to provision desktops, management is greatly simplified. Disk data is streamed dynamically and in real time from a single shared image, providing machine image consistency and enabling large pools of desktops to completely change their configuration, applications, and even OS in the time it takes them to reboot. Because all desktops are bitwise compatible, the 5-15% patch failure rate vanishes, and support costs are greatly reduced. 2. Storage. Since no desktop changes would be saved, block-based image sharing technology could be applied to reduce storage. VMware already owned an image sharing technology called Linked Clones, which had been used for many years to reduce the hardware costs of using VMware Workstation. VMware integrated Linked Clones with VMware View Composer and introduced it to customers as the preferred method of provisioning desktops for VMware Horizon View. With Linked Clones, the cloned desktop uses the virtual disk of the parent virtual machine from which it was cloned. This dramatically reduces the time needed to set up a virtual machine, and the amount of disk space the clone uses. When the desktop is created as a Linked Clone, a Delta Disk is "linked" to the replica disk. The Delta Disk is where all changes or differences between the parent VM and the cloned desktop are stored.

5 Citrix also owned shared image technology. Citrix Provisioning Services (PVS) has been used for years to manage terminal server farms. It was a natural step for Citrix to make PVS a provisioning option for Citrix XenDesktop. Like View Composer and Linked Clones, PVS shares a single shared disk image (vdisk) rather than copying full images to individual machines. This enables organizations to reduce the number of disk images that they manage. PVS uses a cache file to capture the changes to the underlying OS when running in "Standard" mode. There is also a "Private" mode that enables you to save changes to a vdisk in the disk itself. Generally, administrators use two vdisk images for a build. One vdisk image is in standard mode streaming to the desktops. The other vdisk image is updated for new revisions. The two vdisk images either have to be kept in sync, or clones need to be made each time an update is performed. For VDI, this process can be tedious compared to other solutions, but the ability to use either local storage or SAN storage is a huge benefit. Citrix also offers a similar image sharing technology called Machine Creation Services (MCS) for customers who want to provision only VDI desktops. Early VDI adopters were eager to implement the non-persistent virtual desktop model because of its potential to reduce storage costs and simplify image management. It proved adequate for users who required the same applications and who didn t mind that their customizations were lost after each use. Call centers, kiosks, and static labs that rarely changed were ideal use cases. However, these use cases accounted for only 5-7% of all desktops. For end users who expected their virtual desktops to act like PCs and preserve settings and user-installed applications, and for IT administrators who needed to frequently reconfigure desktops to meet the needs of different departments, use cases, projects, and business units, non-persistent desktops proved inadequate.

6 The Non-Persistent Desktop Plus Point Tool Era To address the need for desktop customization and personalization while retaining the efficient resource utilization and single image patching benefits of non-persistent desktops, Citrix and VMware embarked on strategies to integrate and/or acquire third-party solutions. By adding profile management, user virtualization, and application virtualization technologies on top of their existing non-persistent desktop models, customers would in theory get everything they needed. User virtualization tools would capture and restore the user-installed applications, ITinstalled one-off applications, and application plug-ins and add-ins that live outside of a user profile, and therefore cannot be captured by profile management technology. Citrix acquired RingCube, whose technology became Citrix Personal vdisk. Profile management tools would capture and restore the user settings and customizations that were lost when non-persistent desktops were reset. VMware acquired RTO Software, whose technology became VMware View Persona. Citrix acquired Sepago, whose technology became Citrix User Profile Management. Application virtualization tools would enable different applications to be delivered to desktops based on the needs of each user by separating the applications from the shared base/parent/master image. VMware acquired Thinstall, whose technology became VMware ThinApp. Citrix recommends Microsoft App-V through its strategic relationship with Microsoft. Image management and storage optimization tools would enable desktops to be provisioned from a common base image to reduce storage costs and simplify patch management. VMware combined Linked Clones with VMware View

7 Composer. Citrix integrated PVS with Citrix XenDesktop, and later launched Machine Creation Services (MCS) to offer a simpler provisioning solution designed specifically for VDI. This model became the most common desktop virtualization model, despite being fraught with complexity and limitations that will be discussed later. The Layering Era More recently, a new, unified solution for provisioning and managing virtual desktops and applications has taken hold, replacing the need for non-persistent desktops managed by point tools. Hundreds of organizations are now using desktop layering technology from vendors like Unidesk to provision persistent and nonpersistent desktops from a single shared Windows OS layer, any number of shared Application layers, and unique Personalization (User) layers. With desktop layering technology, the old debate of persistent vs. non-persistent desktops becomes obsolete. Layered desktops can be persistent or non-persistent. Yet, both types of desktops are as storage-efficient as non-persistent desktops provisioned with block-based image sharing technology. Layered desktops are assigned to specific users or roles at first login. Desktops share a single instance of the Windows OS layer and all Application layers, so patches and updates are applied only once and storage utilization is greatly reduced. Because layering is based on file system and registry (C:) virtualization not block-based image cloning all desktop

8 customizations, including applications and plug-ins that are installed by IT administrators and end users, are sustained. Base layers can be patched as often as IT wants without affecting the upper layers. With layering, the only difference between persistent and non-persistent desktops is whether the Personalization layer is reset after each use. If a desktop is configured as persistent, the Personalization layer is left intact. If a desktop is configured as non-persistent, the Personalization layer is wiped clean. The decision of whether to deploy persistent and nonpersistent desktops can now be based solely on use case, since both require minimal storage, and both are built using common layers that only need to be patched once. Layering software like Unidesk integrates with the leading brokers and the leading hypervisor so that the brokers are still used for virtual desktop access, but provisioning, application virtualization, personalization, and storage optimization are handled by the layering console.

9 Debunking Myths and Misconceptions Vendors, bloggers, and analysts have made the persistent/non-persistent VDI discussion more confusing by using similar terms to describe different approaches. Before we dive deeper on technology, use cases, and pros and cons of the two most common models, let s clear up some common misconceptions. VMware s Persistent Disk is the Same as a Persistent Desktop Myth. VMware s decision to rename the User Data Disk to the Persistent Disk has made some IT administrators think they are deploying persistent virtual desktops capable of capturing all customizations. This is not the case. When VMware Linked Clones and View Composer are used to provision desktops for VMware Horizon View, there are actually four different types of disks: Delta Disk: The Delta Disk is where all changes to a desktop are stored. The Delta Disk grows over time until the desktop is recomposed (usually to apply a Windows patch or application update). At this point, the Delta Disk becomes invalid, and all changes are lost. Disposable Disk: The Disposable Disk contains all page and temporary files. It gets cleared every time the desktop is rebooted. Internal Disk: The Internal Disk holds the Windows Active Directory machine password, which ensures that the desktop does not lose its domain trust when the desktop is recomposed. Persistent Disk: The Persistent Disk is optional and is assigned at the pool level. It is typically used to redirect file saves to a D: drive so that data can be preserved and shared. Files redirected to the Persistent Disk are not lost during a desktop recompose or reboot. It is also common for administrators to redirect Windows profiles to the Persistent Disk. User-installed applications, however, don t typically work with the Persistent Disk, since too many Windows apps write to the registry and hard-code C: directory names. The Persistent Disk also doesn t capture other information that does not take kindly to redirection computer name, MAC address, volume serial number, and disk signature. Without these, strange application behavior is likely to occur.

10 It is important to note that data and profiles will only survive a desktop recompose operation if the user or administrator explicitly saves them on the Persistent Disk. This is why complaints from end users about applications, settings, and files being lost when IT recomposes desktops are so common. To avoid this end user backlash, IT organizations often delay desktop recomposes. This results in three problems: 1. The Delta Disk grows in size, using up more storage. 2. Windows patches aren t applied as often as they should. 3. Updating applications that are bundled as part of the Windows image takes much longer than end users would like. Persistent desktops especially persistent desktops managed with layering technology don t have these issues. Full-Sized, Thick Clones Are the Only Way to Deploy Persistent Desktops Myth. Before the advent of layering technology, the only way to create persistent desktops was to allocate full-sized VMs, each with their own copies of Windows and applications. This is why many people use persistent desktops, 1:1 desktops, full clones, and thickprovisioned desktops as interchangeable terms. Technology has advanced, however. Persistent desktops can now be created using layers containers of files and registry keys that can be merged into a virtual C: file system. In the world of layering, the Windows OS layer and Application layers are shared across all desktops persistent and non-persistent alike. Persistent desktops are distinguished from non-persistent desktops by a Personalization layer (aka User layer) that captures all customizations. Unlike the VMware Persistent Disk, the Personalization layer remains unchanged when underlying Windows and Application layers are patched and the desktops are rebuilt. State of Ohio Department of Developmental Disabilities is proof that 1,400 persistent desktops can be created on a small storage footprint, and be managed from a shared set of single instance, patch-once layers. Persistent Desktops Require a Lot of Storage Myth. Before layering technology was introduced, this was correct. Full clones were the only way to provision true persistent desktops without the fear of losing user customizations every time the desktops were patched. Having to allocate 40 GB or more of disk space for every clone to store its own copy of Windows and applications often made VDI cost-prohibitive. Fortunately, this is no longer true. Desktop layering technology enables persistent desktops to be created on 70-80% less storage capacity than full clone virtual desktops. If you combine

11 layering with next-generation flash-enabled disk arrays that offer in-line de-duplication and compression capabilities, the storage reduction can exceed 90%. Construction company Egan Co. in the Twin Cities of Minnesota is deploying persistent virtual desktops to all of its knowledge workers using layering technology and flash arrays with deduplication and compression. Egan s CIO reports that their first 200 desktops are only using 500 GBs of storage for an average of 2.5 GB per desktop. Persistent or Non-Persistent Desktops is an All or Nothing Decision Myth. Again, this used to be the case. When the built-in management tools that come with Citrix XenDesktop and VMware Horizon View were the only options for provisioning desktops, you had to choose different technologies and management techniques to deploy persistent and non-persistent desktops and manage images. Often, this setting had to be applied to an entire pool of desktops. If a non-persistent VDI architecture was deployed and later deemed inappropriate, the VDI project became a complete rip-and-replace. With VDI managed by layering software, the underlying technology for non-persistent and persistent desktops is the same. With Unidesk, for example, you simply select the desktop type when you create a desktop. If you want to change the type, just select the other option. Sunrise Health is deploying VDI to 3,000 users. Its desktops are almost equally split between non-persistent (nursing stations, kiosks) and persistent (clinicians, staff) using the same layering foundation. Here is how four educational institutions are implementing non-persistent and persistent virtual desktops using the same layering technology: Colby Sawyer College. Colby-Sawyer virtualized its faculty and staff desktops first. They knew that persistent desktops would be required to satisfy the heavy customization requirements of its professors. Mercer University. Mercer has almost 1000 virtual lab desktops in production to deliver on its Borderless Classroom vision. Unidesk is used to provision the non-persistent desktops that are accessed through VMware Horizon View. Tennessee Tech University. TTU has a mix of persistent and non-persistent desktops for labs, engineering classrooms, the health center, and staff, all provisioned from 1 gold OS layer. William Woods University. William Woods deployment is completely non-persistent, since its goal was to make its lab desktops accessible to students from any location.

12 Analyzing the Two Most Common Desktop Models Let s finish by taking a more detailed look at the use cases, technologies, and pros and cons of the two most common virtual desktop provisioning and management models now in use: Non-Persistent Desktops with Point Tool Management Persistent and Non-Persistent Desktops with Desktop Layering Non-Persistent Desktops with Point Tool Management The most successful implementations of the non-persistent model with management by point tools are environments that require high availability and have simple application needs. The classic use case is the large call center - hundreds or thousands of desktops that all have the same set of applications and must be available 18 to 24 hours a day. The key to being successful with non-persistent desktops is that the applications are either the same for all desktops, or they can be delivered using application streaming or traditional application virtualization. Use Cases Call Centers Static Classrooms, Student Labs, and Training Rooms Libraries Task Workers Kiosks Technologies VMware View Composer, Citrix Provisioning Server, Citrix Machine Creation Services VMware Linked Clones, Citrix vdisk VMware Thin App, Microsoft App-V VMware View Persona, Citrix User Profile Management Citrix Personal vdisk Desktop Provisioning Image Sharing and Storage Optimization Application Virtualization and Streaming Profile Management User Virtualization Application Delivery For any desktop model, application delivery is the big challenge. In this model, applications can be delivered and updated in two ways: Included in the base image. Streamed or virtualized with Microsoft App-V or VMware ThinApp.

13 Including applications in the base image is not advisable except for the simplest use cases. Otherwise, you ll face several challenges: Building every possible app into a single Windows image would force you to license every app for every user. Having to update the master image every time an application needs to be updated will impact all desktops. Creating different Windows images with different combinations of apps will create patching inefficiencies and drive up the operational costs of VDI. For these reasons, most organizations opt for application virtualization. With Microsoft App-V, streaming servers serve virtualized applications to desktops. The desktop has a client with a large cache. You can either load the whole application at run time or pre-cache the application on the desktops. App-V has a concept of "sequencing" an application where it figures out the files that are needed when you first run the application. Those files are streamed to the desktop first when the application is launched to speed up launch times. ThinApp works slightly differently in that it encapsulates the entire streaming file into an executable that can be run from a file server or copied locally to the desktop. One benefit of these traditional application virtualization products is that they isolate applications from each other, enabling you to run conflicting applications side-by-side. Another benefit is that applications can be dynamically assigned to users as they logon. Traditional application virtualization also has several drawbacks: It is difficult and time-consuming. By the time you ve finished the desktop setup, pre-scans, post-scans, scripting workarounds, Windows registry changes, and deployment to 50 desktops, you ll find a full day has passed. Or more. It s not unusual to spend a week virtualizing a single app. And that s if you re an expert. Not all apps can be virtualized. Even if you are an expert, there s a long list of apps that cannot be virtualized with traditional app virtualization tools. Apps with system services and boot time drivers (e.g. antivirus, printers, scanners, etc.), homegrown apps, and apps with complex Setup procedures often won t work.

14 Isolated apps can t cross-communicate. Application isolation puts apps into their own protective bubbles, effectively hiding them from Windows and other apps. This is perfect for running multiple versions of the same software (e.g. Java or Microsoft Access) on the same desktop. But it s a showstopper for the other 95% of apps that need to share data, link to each other, and cross-communicate. Pros and Cons The Pros of non-persistent desktops with point tool management: High Availability If a host or storage array fails, users can simply logon to another desktop. There are still parts of the environment that can cause an outage, but with all the desktops being the same, it is easier to provide DR with a mirrored site. Good Manageability Management of the Windows OS is efficient, as long as you don t create multiple images. Any patches/updates to the central image are deployed to all cloned desktops. If applications are the same for all desktops, application manageability is also excellent. If apps must be different, manageability depends on the ability to virtualize the applications and the skill and size of your IT staff. Minimal Storage Footprint Both VMware View Composer with Linked Clones and Citrix Provisioning Services (PVS) with vdisk greatly reduce storage requirements. PVS can even be used with local storage on the PVS servers. Fast Deployment of Simple Apps Using application streaming/virtualization, applications can be deployed very quickly to all desktops in the environment. For applications that are not easily virtualized, this becomes harder and may result in OS image sprawl. Fast Deployment of New Desktops Desktops can be deployed very quickly given that the OS and the parent/master desktop are already built. Simple Desktop Refresh Desktops can be reset to a pristine state with a simple reboot. This is well-suited for student labs, some classrooms, kiosks, and training facilities. The Cons of non-persistent desktops with point tool management: Application Delivery There will be a large percentage of applications that take too much time to package with traditional app streaming/virtualization tools, and a smaller percentage that will not work at all due to the use of drivers, the way they implement licensing checks, and their designs not being compatible with isolation. Image Sprawl Because of the challenges with app virtualization, you ll have to fall back to delivering apps as part of the Windows image. If your users have diverse application requirements, this will result in many images. The more images that are required, the more time and effort it takes to patch and update the images.

15 User-Installed Applications Enabling users to install their own applications or IT to install one-off apps on behalf of users is difficult with this model. VMware offers no native capability. Citrix offers Personal vdisk, which creates a persistent layer on top of the PVS image for each desktop. When users and IT admins install applications into the Personal vdisk, the apps survive base image updates. However, most organizations using Personal vdisk encounter the same inefficiencies as including apps in the base image, since delivering and updating an app used by 20 people would require installing and patching the app 20 times in 20 Personal vdisks. Complexity and Cost Many lean IT organizations struggle to implement and manage non-persistent desktops with the mix of point tools. The complexity of this model often results in VDI being managed by Level 2 and 3 server administrators, rather than the Level 1 admins who managed PCs. This adds unforeseen costs in the form of hiring outside consultants, or diverts senior IT staff from forward-facing, strategic projects. End User Confidence Users will often lose settings, plug-ins, or data every time Windows is updated and desktops are recomposed because data redirection and profile management cannot capture everything. End user productivity and confidence will suffer when they have to manually reconfigure their desktops. The service desk will also spend more time taking support calls. Persistent and Non-Persistent Desktops with Desktop Layering Desktop layering offers the flexibility of creating persistent or non-persistent desktops. It also combines desktop provisioning, application virtualization, image management, personalization, and storage optimization into one, easy-to-use technology platform. For these two reasons, layering is being rapidly adopted by Citrix XenDesktop and VMware Horizon View customers as an alternative to non-persistent desktops managed by point tools. Use Cases Office staff / knowledge workers Professional workers such as lawyers, engineers, and architects Healthcare clinicians and staff Students whose desktops stay with them all 4 years Classrooms, student labs, and training rooms where apps change often Developers

16 Technology Desktop Layering (e.g. Unidesk) Storage Optimization Desktop Provisioning Image Sharing Application Virtualization Profile Management User Virtualization Application Delivery In the layering model, applications can be delivered and updated in two ways: Included in the base OS layer. Virtualized as an Application layer. Virtualizing an application as a layer is fast and simple an administrator selects an Installation virtual machine, logs onto the machine, installs the application (doing whatever they would normally do to install the app on a regular desktop), and clicks Finalize. The application layer is now available to be assigned to any desktop on top of the base OS layer. Because the layering process is so fast and easy and almost any application can be layered, most customers keep the base OS layer clean, and deliver applications as independent layers. Virtualizing applications with layering technology has many advantages: It s fast and easy. Layering often takes less than 15 minutes. The process is so simple that many customers have interns layering applications. It works with 99.5% of applications. Apps with system services and boot time drivers (e.g. antivirus, printers, scanners, etc.), homegrown apps, and apps with complex Setup procedures can all be layered. Apps can cross-communicate. Layered apps are not isolated. They appear to Windows, and to other apps, as if they are natively installed. As a result, customers who rely on add-ins and plug-ins for Microsoft Office and other core applications can virtualize the plug-ins as separate layers to make patching and updating fast and easy. Yet they don t have to worry that the plug-ins won t work with their base application. The main drawback of application layering is that layers cannot yet be dynamically assigned to users as they logon. Desktops must be rebooted before the layered apps appear. In addition, layered applications are not isolated. However, layering works seamlessly with traditional application virtualization technology if isolation is needed many customers deliver ThinApp packages in layers to get the benefits of central management, assignment, versioning, and layer rollback.

17 Pros and Cons The Pros of persistent and non-persistent desktops with desktop layering: Good Manageability 1 gold OS layer can be used for all non-persistent and persistent desktops for patch-once simplicity. High Availability Desktop layering uses the same hypervisor APIs as the brokering management tools, and adds the ability to snapshot and version OS, Application, and Personalization layers for easy rollback and recovery. Application Delivery Almost all apps can be layered in minutes, without deep packaging expertise. This is probably the single biggest benefit of layering the ability to quickly and easily deliver different sets of apps to different desktops, without the limitations of first-generation app virtualization tools. Minimal Storage Footprint Desktop layering greatly reduces storage requirements for both persistent and non-persistent desktops. It also supports the use of local storage. Fast Desktop Deployment Desktops can be deployed very quickly just by selecting which layers are needed. Templates, which pre-select OS and App layers based on department or job function, can also be used to further speed up provisioning. Simple Desktop Refresh If the desktop is set to be non-persistent, it can be reset to a pristine state with a simple reboot. Because the user layer is simply thrown out and no recompose of the desktop is required, this is often faster than non-persistent desktops implemented with VMware View Composer and Linked Clones and Citrix PVS/MCS. User-Installed Applications End users (if they are given Admin rights) and IT admins can install one-off applications into the Personalization layer and the apps will survive base layer updates. If it turns out that 20 people need the same app, the app can be virtualized by IT as an App layer in minutes and assigned to all 20 desktops. From that point on, it only needs to be patched and updated once. Less Cost and Complexity Many lean IT organizations find layering simpler than trying to implement and manage non-persistent desktops with the mix of point tools. Level 1 administrators can manage daily desktop operations, freeing more senior IT staff to focus on forward-facing, strategic projects. End User Confidence End users won t be able to tell when Windows or applications have been patched or updated. All of their icons, shortcuts, screen layouts, personal apps, and plug-ins will be the same. The Cons of persistent and non-persistent desktops with desktop layering: No Half-Persistence With layering, desktops are either persistent (all customizations are captured and preserved in the Personalization layer) or non-persistent (the Personalization layer is cleared after each use so that nothing is preserved). If you need to provide desktops that retain a subset of personal settings, you will need to create non-persistent layered desktops and add roaming profiles or a profile management tool.

18 Licensing Cost - Adding a third party layering solution increases VDI costs. However, 600 layering customers attest that the additional cost is usually recouped within 3 months based on the persistent desktop storage savings and the operational cost savings from patching Windows only once, virtualizing all apps in minutes, and enabling Level 1 staff to manage and support VDI. Summary You should now have a clearer understanding of what persistent and non-persistent virtual desktops are, what they are not, what technologies can be used to implement them, and how customers are succeeding with both desktop types. You should also realize that VDI innovations such as desktop layering and flash-optimized storage have rendered the old debate obsolete. Now, the decision to implement nonpersistent or persistent desktops should be based solely on use case, not technology limitations or cost impact. Unidesk Corporation, 313 Boston Post Road West, Marlborough, MA USA Tel Fax Copyright 2014 Unidesk Corp. All rights reserved. This product is protected by U.S. and international copyright and intellectual property laws. Unidesk is a registered trademark of Unidesk Corp. in the United States and/or other jurisdictions. All other marks and names mentioned herein may be trademarks of their respective companies. Item No: UNI-EB-PERSISTENT-NON-VDI