Desktop as a Service is not VDI in the cloud, nor is it XenApp/RDS in the cloud. Those are products and marketing terms. Whew, there, I said it…
I have to say I am somewhat amazed that almost two years after the releases of Windows 7 and Windows Server 2008 R2 there are many “experts” in the desktop virtualization business that still want to argue the case that VDI is the best alternative for all desktop virtualization solutions, including the emerging Desktop as a Service market. This almost dogmatic acceptance of “the one true way” presents an incredible disservice to both the buyer—who wants a cost effective solution to their desktop challenges—and the technology professionals—who care about scalability and the cost of services. By not understanding all of the desktop virtualization options for this emerging space, it will be difficult to develop a solution that works for the customer and the service provide. Yes, “the customer is always right” but let’s educate them a little before we let them make the final “right” decision.
Overall there are many different desktop virtualization models to consider, but I want to focus on the relationship of the big three for this service provider centric post; Terminal Services (aka: RDS, Hosted Shared Desktop, or Session-based Virtualization), VDI and Desktop as a Service. At a purely technical layer, they are not that different, especially now that Windows 7 and Windows Server 2008 R2 operating systems are finally the exact same code base. Since the client and server offerings from Microsoft are basically different product lines based on the same OS, their desktops can look and behave exactly the same, support the exact same set of APIs and the same device drivers (printer problems anyone?). This means that from a technical perspective all applications and any associated peripheral devices can be equally supported within the Windows 7 or Windows Server 2008 R2 based desktops.
To further demonstrate the difference between the market positioning of VDI vs. Terminal Services/RDS and the technical reality that needs to be embraced when looking at all of the options, Windows Server 2008 R2 can be dedicated to a single user with full administrator level control over their own machine. This is effectively VDI and not a Hosted Shared, or even session-based model. The only real difference is that it uses the server OS instead of the client OS. I usually refer to this as a “Hosted Personal” desktop. Several Citrix Service Providers are leveraging this approach in order to provide that admin level of ownership for users of hosted desktops in those few cases where it is deemed absolutely necessary, but in a Microsoft SPLA compliant solution. As with VDI based on the client OS (ignoring licensing for now) there is of course a higher cost to both the service provider and the customer when using this model because of higher infrastructure costs and lower economies of scale when compared to a Hosted Shared approach. The point is, technically, as a desktop or application delivery platform client OS or server OS is irrelevant since they are the same underlying system.
As the only recognized leader in the desktop virtualization space according to IDC, Citrix and our partners have spoken about FlexCast capabilities for a while now in order to educate IT buyers regarding the different models they should consider for different enterprise IT desktop virtualization scenarios. The two most familiar and widely deployed FlexCast desktop delivery models are Hosted VDI (VDI) and Hosted Shared (XenApp on RDS), based on Microsoft Windows Client and Server operating systems respectively.
In traditional enterprise IT deployments, a single infrastructure is hosted on premise for that specific organization, and they own (or lease) all of the infrastructure and software licenses. The guidance in this scenario has generally pointed to Hosted Shared desktops for simple task worker scenarios and Hosted VDI for almost every other use case. Naturally, there is a tendency to map these enterprise definitions and their associated mindset to the emerging Desktop as a Service market. Unfortunately, this confuses the Desktop as a Service conversation with technological myths that evolved in the enterprise space rather than looking at broader needs of the hosted desktop customer who is often quite different. Here we are seeing the full range of customer profiles, everything from the one-man shop, the SMB and into the enterprise.
The question once again comes down to “why would you use one desktop virtualization approach over the other”? For service providers who are actually making money today (primarily by selling to small to medium sized businesses) the primary answer is COST OF SERVICES. How does a service provider keep the cost of desktop services low enough to even begin to meet subscriber expectations set by web services and web-based SaaS offerings? Through the same basic mechanisms used for these other services of course; economies of scale provided through high-density workloads, secure multi-tenancy, and efficient back-end management of as many shared resources as their business can leverage for their chosen user base.
So in light of all of this “what is Desktop as a Service”?
Well an emerging definition for Desktop as a Service can be summed up as…
A desktop delivery model that leverages various virtualization technologies, enabling service providers to 1) host, manage and integrate applications into desktops within a secure, shared multi-tenant datacenter, and 2) to provide the customer subscription based access to those managed desktops and applications.
Now to the meat of the discussion (yep, you play a role here as well)!
There continues to be much discussion around the different requirements for a successful Desktop as a Service solution, and rightly so since this is an early stage emerging market. We have recently posted the latest version of The Citrix Reference Architecture for Multi-tenant Desktop as a Service, which reflects a real world view of how this service business is currently enabled by Citrix and our strategic partners as delivered by a large number of active Citrix Service Providers. This is a living document that will evolve as the end-subscriber requirements, the service provider business models, and the resulting capabilities of the referenced systems evolve within this space. It should be obvious that the integration of new projects like Olympus and our work with OpenStack, on-going acquisitions like the Cortex Control Panel and more recently the Cloud.com teams, as well as vital partner capabilities like those enabled by Microsoft and a long cast of others will continue to influence further revisions of the architecture. Needless to say, at this stage of the market there are many exciting concepts and capabilities being discovered, invented, vetted, and assimilated into this delivery model, and there are many opinions regarding what needs to be addressed. Some of the major points can be found in a good post by Jason Langone (a former Citrix employee). Although you will see his definition of Desktop as a Service kind of falls into the “VDI in the cloud” trap, he brings to bare many technical points that are being taken into consideration by several vendors (including Citrix and our partners). Specifically concerning multi-tenant infrastructure and management as the Desktop as a Service market evolves to address enterprise customer isolation and delegated administration requirements.
Many of the major hardware, software vendors, systems integrators and consultants currently engaged in the enterprise desktop virtualization space are looking at Desktop as a Service as an attractive adjacency to their businesses and it continues to be a fun ride working with all of them as these offerings evolve. What we need as vendors, from you our channel partners and customers, is the continued dialog around how this space needs to evolve and what the business and technical benefits and challenges are as they present themselves.
So what do you say?
Anyone want to talk about…
… why the argument between VDI and Terminal Services continues even though the OS is the same?
… the definition of Desktop as a Service?
… technical challenges inherent in multi-tenancy for Windows based solutions?
… anything else relevant to this post?
Oh yes, and what better way to engage in some of these discussions than to join me and John D’Agati — on Wednesday August 17th at 11:00 AM EST for a live “ask the experts” webinar.
This session is designed for you, so you can get as much out of the reference architecture catalog as possible in order to build the best possible multi-tenant DaaS and SaaS solution for your business. Just read the document and related blog posts ahead of the event and think about how it applies to your business and services architecture. Come armed with your reference architecture specific questions, ideas and challenges. Moreover, let us know your key questions ahead of time so we can tailor the session to address the most relevant questions and concepts for the entire CSP community. If you have something you want covered, send an e-mail or post on LinkedIn.
Wednesday, August 17, 2011
11:00 AM – 12:00 PM EST