Desktop as a Service: Go virtual or not?

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Note: Through Jan. 4, we are posting the top 10 posts of 2012. This is #2 and was originally published on Feb. 17, 2012.

Overview of ways to deliver cloud-based user workplace, and current challenges

Cloud terminology is already complex enough with its IaaS, SaaS, PaaS, BPaaS; so now we have one more term contributing to the overall confusion with cloud-related services. It is desktop as a service (DaaS). You might say “Well, it is just another buzz word to help marketing guys in selling virtualization” and probably you are right.

The most common description of desktop as a service is ready-to-consume Virtual Desktop Infrastructure (VDI) hosted and managed by a third-party cloud service provider accessible from any device anywhere. DaaS has multi-tenant architecture and is purchased on a subscription basis. In this delivery model, the service provider manages the back-end infrastructure—hypervisors, storage, networks, security—while the customer maintains responsibility for user data, desktop management, and software licensing.

This definition works well for a general explanation, but if you have to build DaaS for a service provider, you should consider multiple factors as: flexibility, customization, cost and licensing. Here is my attempt in guiding you through five possible delivery models:

  1. DaaS with traditional VDI for Windows Virtual Desktop in the data center

Technologies in support of this model are Desktone, Citrix XenDesktop, VMware View, and Virtual Bridges VERDE.


    • Highest level of desktop customization per user or group of users
    • Low operational cost

Disadvantage: Microsoft licensing limitation:

    • No Service Provider License Agreement (SPLA) for Windows Desktop OS
    • Required Software Assurance (SA) or Virtual Desktop Access (VDA) Licenses to be owned by customer
    • Charging on monthly basis with at least one-year contract, and no true pay-as-you-go (PAYG).

In addition to these disadvantages, service providers are not allowed to host virtual desktops of more than one customer on the same hypervisor host. Desktops can be offered in blocks of virtual machines (VMs). This means that the service provider could target only medium and large businesses and should consider multiple server hardware configurations.

User experience is dependant on storage performance, network availability, bandwidth and latency.

  1. DaaS with Traditional VDI for Linux Desktop in the data center

Technologies in support of this model are Virtual Bridges VERDE and Desktone.


    • Highest level of desktop customization per user or group of users
    • Low operational cost
    • No Microsoft license cost, allows PAYG charging
    • Meets all use cases from consumer market to enterprise


  • Remote Access Protocols (for example, SPICE) are yet to meet the performance and capabilities of industry-leading Citrix HDX and Teradici PCoIP.
  • No support for high performance remote access protocols on smartphones and tablets
  • Applications, which are not supported by Linux, require additional application delivery infrastructure such as Citrix XenApp.
  • User experience is dependant on storage performance, network availability, bandwidth and latency.
  1. DaaS with Client Side VDI (or desktop hypervisor)

Technologies in support of this model are Virtual Bridges VERDE, Citrix XenClient, and Virtual Computer NxTop.

With this architecture virtual desktop is delivered from gold image in the data center, but virtual machine is running on a client workstation or notebook. Virtual machine and user data are periodically synchronized and backed up with a copy in the data center.


  • Fewer servers and storage are in the data center compared to traditional VDI, so less capital investment.
  • No network dependency—the virtual machine is accessed while disconnected from the network.
  • Only the Microsoft Volume License is required when running up to one Windows virtual desktop per user
  • Security is improved with built-in disk encryption, centrally controlled policy for device and VM deactivation if endpoint is lost or not connected to data center for period of time.


  • Endpoint devices are limited to workstations and notebooks only with specific hardware requirements.
  • Some solutions have limited hardware compatibility list.
  • Operational cost is higher because on-site support activities are required to repair endpoint hardware breaks.
  1. Daas with Hosted Shared Windows Desktop (also known as Terminal Services)

Technology in support of this model is Citrix XenApp.


  • Cost is low cost compared to VDI.
  • Offers existing Microsoft SPLA licensing and true PAYG.
  • Suitable for small, medium, and large businesses.


  • Users are sharing session on server, limited desktop customization, therefore mostly suitable for task or data entry workers.
  • High level of customization could be achieved by user data and profile management and on-demand application delivery.
  • Depends on network performance and availability.
  1. DaaS with traditional PC (also known as well-managed desktop)

Technologies in support of this mode are IBM Tivoli Endpoint Manager and Novell ZENworks.

This model represents centralized, distributed, or hybrid architecture where desktop OS is installed and managed on user workstation or notebook. It is very similar to client-side VDI (desktop hypervisor), with the difference being that client-side VDI is an all-in-one solution, while traditional PC DaaS consists of multiple components, for: OS and application delivery; OS and application configuration, updates and patching; security; monitoring; and inventory.

DaaS with traditional PC does not look “cloudy,” but if we use cloud to enable user self-service, standardize, automate, and optimize operational and business support services, then we have real desktop as a service compared to just managed desktop services.


  • Moderate capital investment
  • Existing Microsoft Service Provider License Model
  • Network independent
  • High-end user experience
  • Support for both Windows and Linux desktop OS
  • Support for a variety of use cases from task workers to power users


  • Has high operational cost.
  • Desktop on workstation or notebook only.
  • Additional cost exists for hardware breaks and fixes (onsite support or logistics).
  • Longer time is needed to deliver and recover OS and applications compared to online and offline virtual desktop.
  • Additional hardware and software are required to ensure data protection if device is lost or stolen.
  • User OS and data backup/restore infrastructure is mandatory.


There are multiple ways to deliver desktop as a service, depending on service provider and customer requirements. Answering the biggest question “Go virtual or not?” is still a challenge.

Desktop virtualization advantages are obvious and there is clear demand for virtual desktop “to go.”  Unfortunately service provider initiatives in answering this demand are stopped or greatly limited by Microsoft licensing restrictions. Microsoft is not an enemy of desktop cloud, but does use its lead position to shape and control the market until it is ready with its own desktop cloud; so, the only way to push Microsoft forward is through this message to service providers: “Yes, go virtual with Linux desktop.” (Promote Linux VDI.)


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