Citrix XenApp vs XenDesktop: How to Decide

Posted by Tom Rose on May 23, 2016

xenapp-vs-xendesktop.pngShared hosted desktops and published apps with Citrix XenApp? Or full virtual machines for every user with Citrix XenDesktop? The Citrix XenApp vs XenDesktop decision used to be pretty clear. But with new application layering innovations that can deliver unique apps and personalization in real-time to every XenApp user, the line between traditional server based computing (XenApp) and VDI (XenDesktop) has been blurred.

This blog summarizes the traditional differences between XenApp and XenDesktop, explains how Unidesk application management software changes the equation, and then provides a new decision matrix for the two Citrix hosted workspace solutions, so you can decide which is right for you, your users, and your business.

Traditional Differences Between XenApp and XenDesktop

Many people think that XenApp is for delivering hosted Windows apps and XenDesktop is for delivering hosted Windows desktops. Citrix's naming scheme certainly encourages this thinking. However, XenApp can also deliver full desktops as well.

The major difference between the two is the type of desktop. XenApp delivers a one-to-many Windows Server (e.g. Windows Server 2008 or 2012) machine that is shared by many users. XenDesktop delivers a one-to-one Windows desktop machine (e.g. Windows 7 or 10) that is used by a single user.

At a high level, this fundamental difference has meant:

  1. XenApp users share the CPU, GPU, memory, and disk resources with all of the other users on the same server. XenDesktop users get their own private CPU, GPU, memory, and disk, leveraging the hypervisor's ability to allocate, isolate, and protect these resources on a per VM basis.
  2. XenApp users get a Windows Server look and feel (unless the Windows Desktop Experience feature is used). XenDesktop users get a Windows desktop look and feel.
  3. XenApp users share access to all of the applications installed by IT on the XenApp server they are logging into (i.e. if 200 users logon to the same XenApp server, all 200 users get the same apps). XenDesktop users get access only to the apps installed on their individual desktops (i.e. each user can have their own unique apps).
  4. XenApp users can be given a minimal amount of personalization if IT uses a profile management tool to restore their settings each time they logon. XenDesktop users can be given full personalization, including one-off apps and plug-ins if IT assigns a persistent virtual desktop to each user.

These last two differences are why XenApp customers often start to consider XenDesktop and VDI: most users need different sets of apps and want deeper levels of personalization.

How Unidesk Blurs the Line

What if XenApp could deliver one-off and departmental apps to every user as well as full personalization on a per session basis? Wouldn't it be easier then to leverage XenApp for all apps and all users rather than deploy a new VDI environment with XenDesktop?

Citrix has laid the groundwork for this by developing both products around a common architecture:

  • XenApp and XenDesktop both use Citrix Receiver to provide access to Windows workspaces from any device, including thin clients, PCs, tablets, and BYOD devices.
  • XenApp and XenDesktop both leverage the proven Citrix HDX protocol for secure, high performance remote display.
  • XenApp and XenDesktop are both based on the same Flexcast Management Architecture (FMA), enabling both to be managed from the Citrix Studio management console.

All that's missing is the custom app delivery and personalization capabilities. This is exactly what Unidesk Elastic Layering™ and Session Container™ innovations bring to XenApp.

unidesk-elastic-layering-session-containers.pngTogether, Unidesk Elastic Layering™ and Session Containers™ enable Citrix XenApp to offer the same customizable user experience that was, before, only possible with physical PCs or persistent virtual desktops.

As we're showing this week at Citrix Synergy and as you can see in this first look demo of Elastic Layering, Unidesk application layering innovations can deliver apps and personalization at user logon to individual XenApp sessions based on AD user and group membership. The virtual disk containers representing each app layer are attached to an individual user's session. Unidesk Session Container technology isolates the user session so that other users on the same XenApp server don't see the same apps. For the first time, XenApp can have the look and feel of persistent VDI, making it a fit for all users and use cases.

The New Decision Matrix for XenApp vs XenDesktop

Although these new layering innovations bring XenApp closer to XenDesktop, there are still other considerations to take into account when deciding between the two. We've summarized them here.

When to Choose XenApp

Criteria Requirement Explanation
User personalization Full Profile management tools can be used to restore user settings at XenApp session logon, which is usually sufficient for task workers who require basic personalization. For knowledge workers who want a "My Desktop," PC-like experience, Unidesk persistent layers can now be used to restore apps and plug-ins installed during a specific session (typically by IT) and provide full personalization on a per user basis.
Key, mission-critical apps Yes Delivering apps through XenApp has traditionally been a costly and complex exercise requiring custom images and delivery groups, separate XenApp server "silos," and/or major application virtualization efforts. As a result, only the most important apps that are used by many users are worth the investment to deliver through XenApp. Unidesk Layered Images make the delivery of mission-critical apps through XenApp much easier.
One-off and departmental apps Yes Per above, apps used by one user or a small group of users have not been delivered through XenApp in the past due to the overhead required. Licensing costs also prevented delivery of these apps, since all users sharing the same XenApp server would have access and have to be licensed. Unidesk Elastic Layering now makes it easy to deliver one-off and departmental apps on a per user basis by attaching the virtual disk layers representing each user or group-specific app at logon.
USB compatibility None or partial XenApp supports portable USB devices with HDX Plug-n-Play, but support is limited because changes cannot be made on a shared machine.
Administrative privileges No Administrative privileges are not typically given out to XenApp users because any changes made to the shared Windows Server OS will affect all other XenApp users on the same server. With Unidesk, IT can still logon to an individual user session and install any apps or plug-ins needed by the user. These changes will be stored in the user's writable persistent layer and re-attached every time the user logs on.
Resource-intensive apps Maybe If users use resource-intensive apps, they may impact other XenApp users on the shared virtual machine. XenApp metes out resources with a scheduler much like an operating system, but it is still possible for some users to consume an unfair amount of the shared CPU, GPU, memory, and disk resources. The alternative is to reduce user density (the number of users on each XenApp shared virtual machine).
App compatibility Windows Server support
Some application ISVs only support their apps running on a Windows desktop OS. XenApp is based on a shared Windows Server OS, so apps delivered by XenApp need to be compatible with Windows Server.
Apps or users bound to machine No Some apps hard-code themselves to individual machines (e.g. C: drive dependencies, registry settings written to the wrong hives). Users may also be bound to specific machines for security reasons. Trying to use these kinds of apps may still be problematic in shared XenApp environments.
User density Best The number of users per host is often 10-40% greater in XenApp vs XenDesktop, which means overall costs will be lower.

When to Choose XenDesktop

Criteria Requirement Explanation
User personalization Full Profile management tools can be used to restore personal settings when users logon to their XenDesktop VMs. This is usually sufficient for task workers who require basic personalization. XenDesktop also supports the ability to create persistent virtual desktops for every user, which enables all customizations to be saved, including user-installed apps. Unidesk works with XenDesktop to make full persistence more affordable by sharing the same Windows 7/8/10 OS and application virtual disk layers across many machines. This provides both manage-once efficiency and a major reduction in storage capacity when persistence is needed.
Key, mission-critical apps Yes Many Citrix customers deliver their mission-critical apps to XenDesktop by publishing them from XenApp so that they can be managed once centrally. However, this creates a "double-hop" scenario where users use one remote connection to access their virtual desktops and a second remote connection to access the remote apps. Unidesk can deliver apps to each XenDesktop VM with the appearance of a local install either as part of a Layered Image (before the desktop machine boots) or at logon as an Elastic Layer (in-guest attach).
One-off and departmental apps Yes Since XenDesktop users have their own private machines, apps needed by one user or a small group of users can be delivered by installing them just on each user's machine. Unidesk Elastic Layering makes it much easier to deliver one-off and departmental apps to each XenDesktop user and still manage them all centrally.
USB compatibility Full XenDesktop supports broad USB device support with generic USB redirection.
Administrative privileges Yes Administrative privileges can be given out to XenDesktop users more freely because any changes they make will only affect their virtual machines and not impact other users.
Resource-intensive apps Yes XenDesktop users can use resource-intensive apps without impacting other users because each user has their own dedicated resources. CPU, GPU, memory, and disk can also be boosted on a per user basis to better satisfy this requirement.
App compatibility Windows Server support not needed
XenDesktop delivers a Windows desktop OS, so there is no need for apps delivered by XenDesktop to be compatible with Windows Server.
Apps or users bound to machine Yes Apps that are not "well-behaved" (hard-coded C: dependencies or incorrect registry keys) and users that need to be bound to specific machines are more likely to work with XenDesktop persistent virtual desktops, which more closely mirror the individualized experience of physical PCs.
User density Average The price paid for giving every user their own virtual machine with XenDesktop is that resource consumption is higher. This means the number of users per host will be lower than XenApp, which will result in relatively higher infrastructure costs.

XenApp and XenDesktop: 2 Great Options for Windows Workspace Modernization

With new application layering innovations from Unidesk, both XenApp and XenDesktop can meet users' needs for workspace flexibility and mobility, and IT's needs for compliance, security, operational and capital cost control, and manageability. The decision boils down to what apps do you have in your environment, what are your users' requirements, and what infrastructure have you already invested in?

If you already have a significant XenApp investment, using Unidesk to extend XenApp and replace your remaining PCs with shared hosted desktops might make the most sense.

If you don't have any XenApp and you need a mobile workspace that provides resource isolation for demanding apps, virtual desktops with XenDesktop - with application and image management provided by Unidesk - might be the better option.

What are you going to do in your environment? Let us know by commenting below!

Topics: Citrix XenDesktop, Citrix XenApp, Elastic Layering, Session Container

Posted by Tom Rose on May 23, 2016

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