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What is VDI Anyway?

Posted by jdeweese-esristaff Employee Apr 25, 2019

Often the term "VDI" is used to define ArcGIS Desktop/ArcGIS Pro deployed as a virtual application. The challenge is understanding what specific virtualization technology is actually being referenced when using this term since VDI, or "Virtual Desktop Infrastructure", represents just one of several desktop virtualization options. So, the intent of this article is define the options and differentiate what VDI truly means.

 

ArcGIS Desktop has been delivered virtually for over 20 years using what is referred to as "hosted virtual applications" which includes technologies such as Citrix XenApp (recently renamed to Virtual Apps) and Microsoft Remote Desktop Services (RDS). This approach is referred to as "hosted"  because it is being hosted by a singular operating system which users share by initiating individual user sessions. This technology option represents a many-to-one relationship in terms of users and virtual machines. Further, the shared operating system is a server OS, such as Windows 2016 and not a desktop OS, such as Windows 10. Hosted virtual applications provides a means to share a singular server with multiple users and is an attractive option since since each user doesn't require their own dedicated virtual machine. For this approach, system resources are shared including processors, memory, and GPU and there isn't a practical way to assign resources at the individual user session level.

 

A more recent innovation is to provide individual virtual machines to users as "virtual desktops" where each user accesses a remote desktop deployed with a desktop operating system such as Windows 10. This includes technologies such as Citrix XenDesktop (recently renamed to Virtual Desktops) and VMware Horizon. This approach represents the true meaning of "VDI" as it is defined by a one-to-one relationship between users and virtual machines. Though this approach increases per-user deployment costs, it also provides a more isolated deployment in terms of resources since processors, memory, and GPU resources can be assigned accordingly. The ability to manage GPU resources for the virtual desktops has made this approach an attractive option for ArcGIS Pro which requires a GPU.

 

So, the next time you hear the term "VDI" used for delivering ArcGIS to users, know that this implies that each user is being presented with their own individual Windows desktop virtual machine with a set of assigned resources as opposed to users accessing a singular server-based virtual machine and sharing it with multiple users, including sharing the server's assigned system resources. 

When it comes to technology companies, product renaming and refocus is often inevitable. This recently occurred with Citrix as they have moved away from the "Xen" prefix and have simplified their product portfolio naming to make them easier to understand. For example, the new name for XenApp is "Citrix Virtual Apps" while XenDesktop is now "Citrix Virtual Desktops". These are the two primary products from Citrix that are used to deploy ArcGIS Desktop and ArcGIS Pro as virtualized applications. At the same time, Citrix is changing the associated product versioning and moving to a year and month format, for example:

 

      YYMM = Year and month when the product or component released. For example, a release in August 2018 appears       as 1808.

 

Citrix recently released the latest version of Citrix Virtual Apps and Desktops utilizing these changes and the current release is "Citrix Virtual Apps and Desktops 7 1808.2". This means that XenApp/XenDesktop 7.18 was the last release of the 7.x releases and the new version of "Citrix Virtual Apps" appears to be what XenApp 7.19 would have been and not a major upgrade, though Citrix is constantly evolving their products.

 

Though the naming changes are helpful for understanding product purpose, I don't anticipate much of an impact from these changes at a technical level. Over the last few years Esri has been certifying multiple Citrix releases and the most recent "certified" Citrix release for ArcGIS is XenApp/XenDesktop 7.17. It is likely that the new "Citrix Virtual Apps and Desktops" release, or a subsequent release, will be certified with the next major ArcGIS release so look for updates on the associated ArcGIS system requirements pages.

I just returned from the Esri 2018 User Conference and had a great time. During UC, I encountered many questions about ArcGIS Pro virtualization. For the past 20 years I have worked with Esri customers assisting them with deploying ArcMap using virtualization technologies such as RDSH and Citrix XenApp.

 

As customers plan their migrations to ArcGIS Pro, it is important to be aware that it is not merely a matter of upgrading to ArcGIS Pro utilizing the same IT solutions within the current IT infrastructure. That's because ArcGIS Pro has a different set of system requirements and one of the key differences is the requirement for a graphical processing unit (GPU).

 

ArcGIS Pro leverages advanced display technologies such as DirectX and OpenGL which are highly dependent upon a graphics processing capability. This was not an issue in the past with ArcMap in virtualized deployments since ArcMap is GDI-based and for the most part cannot be accelerated by a GPU. However, Because of this specific requirement for ArcGIS Pro, traditional session-based deployment solutions are not the best fit for ArcGIS Pro, and in most cases Esri is recommending the use of virtual desktop infrastructure (VDI) coupled with GPU management technology such as NVIDIA GRID virtual GPU (vGPU) to provide the IT infrastructure to host virtualized ArcGIS Pro desktops.

 

A variety of servers and VDI solutions are available, and the ArcGIS Pro system requirements page reflects which ones have been certified by Esri. Also, be sure to review the On-Premises virtualization documentation to determine how to work with your chosen VDI solution.

 

The key take-away is that infrastructure upgrades will likely be required if ArcGIS Pro is to be delivered using a virtualization platform and will need to include GPU-enabled servers to support the virtualized desktops.