1 Executive Summary

Designing an enterprise-level desktop delivery solution must take into account users, applications, desktops and the underlying infrastructure design. Simply turning every user into a hosted desktop user, while possible, does not align the technical solution to the business challenge.

Instead, a desktop delivery solution must provide users with the best operating environment based on their needs.

 Some users require process-focused applications, while others require a more dynamic environment allowing them to create and customize their work environment as needed.

This document describes the architecture to providing a virtual desktop infrastructure (VDI) at Customer, based on Windows 7 (hosted VM-based desktop) and Windows 2008 R2 (hosted shared desktop). 

The VDI installation is set up to achieve the following objectives:

  • Provide opportunities to work workplace (location) and device independent
  • Provide standardized remote access on a Customer standard workplace
  • Reducing support and maintenance costs through the use of thin clients
  • provide prerequisites for the customer „bring your own“ (BYO) strategy

Our Customer has tested the Citrix XenDesktop solution during approximately one year. On the pilot installation now work about 20 users. It can be assumed that all use scenarios were tested extensively.

The VDI solution is centrally managed and operated by the Customer. The virtual desktop infrastructure is designed initially for about 150 “hosted VM-based desktops” and about 200 “hosted shared desktops”. 

Further expansion for both type of Desktops is possible at any time. Virtual desktops are virtualized on the existing VMWare Infrastructure.

2 Citrix high-level architecture

Unlike a "Fat desktop" solution, the operating system is no longer running on the PC, but on a central "host system" (VMWare Server) in the data center. This means in case of the loss of a central virtualization host (VMWare) are always multiple users simultaneously affected.

Therefore, in a desktop virtualization environment, the individual components are redundant available.
To ensure the high availability in the local area network (LAN) Citrix recommends the following architecture.

3 Customer high-level architecture

4 Citrix XenDesktop Overview and Compoments

4.1 Citrix Xen Desktop Delivery Controller

At a high level, the XenDesktop controller is responsible for:

  • Authenticating users against Active Directory
  • Enumerating available resources
  • Creating registrations for newly started virtual desktops
  • Maintaining an active heartbeat with online virtual desktops

All XenDesktop implementations should have redundant controllers to provide fault tolerance.

4.2 Citrix Provisioning Server

Provisioning Services takes a very different approach from traditional imaging solutions by fundamentally changing the relationship between hardware and the software that runs on it. 

By streaming a single shared disk image (vDisk) rather than copying images to individual machines, Provisioning Services enables organizations to reduce the number of disk images that they manage, even as the number of machines continues to grow, simultaneously providing the efficiencies of a centralized management with the benefits of distributed processing.

4.3 Citrix CloudGateway

CloudGateway enables IT to regain control by unifying the management, control and delivery of apps, devices and data. One of CloudGateway’s key features is the ability to automate user requests, approval workflows and application account provisioning upon approval

4.4 Virtual Desktops

Based on the organization’s characteristics, a one-size-fits-all virtual desktop solution does not align with the overall goals of simplifying the environment and keeping control of costs. Instead, Citrix recommends a mixed environment that focuses on aligning different technologies to specific user requirements, which can be integrated into a single, cohesive solution.

4.4.1 Hosted „VM-based“ Desktops with personal vDisk (XenDesktop)

The personal vDisk feature in XenDesktop retains the single image management of pooled and streamed desktops while allowing people to install applications and change their desktop settings.

Personal vDisks provide this separation by redirecting all changes made on the user's VM to a separate disk (the personal vDisk) attached to the user's VM. The content of the personal vDisk is blended at runtime with the content from the base VM to provide a unified experience. In this way, users can still access applications provisioned by their administrator in the base VM.

Physically, a personal vDisk does not need to be stored with the dedicated pool VM. This frees up high-speed disks for VM storage; the personal vDisk can be placed on a less expensive storage solution, like a file server.

Our Customer use "VM-based" Desktops for Power Users and the management board. For personal installations are 10 Gb "personal vDisk" provided.

4.4.2 Hosted „shared“ desktop (XenApp Server)

Hosted shared desktops can deliver a locked down, streamlined and standardized environment ideally suited for task workers where personalization is not required. Delivering hosted shared virtual desktop requires proper planning and configuration to maximize the scalability of server resources while providing users with an optimized and functional desktop environment.

4.4.3 Remote PC

Remote PC allows an end user to log on remotely to the physical PC in his or her office from virtually anywhere. The Citrix XenDesktop Virtual Desktop Agent on the office PC enables it to register with the XenDesktop Controller and manages the HDX connection between the machine and end user client devices. The Citrix Receiver running on the client device provides access to all of the applications and data on the office PC.
This type of remote connection could be usefull for the the customer CAD workstations.

4.4.4 Mobile/Offline, local VM-based desktop (XenClient)

This type of desktop is for those users who require offline mobility (e.g. laptops). These users require a local installation of the operating system, but the applications are delivered as a network stream with offline mobility enabled. Management and maintenance of the operating system is done remotely while application support is in the data center. The physical desktop model allows the organization to still support the mobile workforce while centralizing application delivery.

4.5 VMWare vSphere virtualisation plattform

Citrix XenDesktop is an enterprise desktop virtualization solution which can be implemented on all major hypervisor platforms such as Citrix XenServer, Microsoft HyperV, and VMware vSphere. Our Customer uses the already existing VMWare Infrastructure.