Desktop as a Service a.k.a. DaaS

This article was originally written as a guest blogger for Intense School IT educational services. During the past few weeks I repeatedly talk about virtual desktop infrastructures (XenDesktop, VDI-in-a-Box), some of the technology involved, features and probably the most important one, use cases. Especially with Windows XP coming to an end, see my previous article on this, this might be a good time to rethink your alternatives when it comes to replacing your (fat) client infrastructure and the accompanying back-end systems that come with it. That being said, there’s another concept I’d like to discuss since it’s closely related to VDI and could prove to be a valid solution for a great deal of use cases out there, especially when it comes to small(er) and mid sized companies. I’m referring to DaaS, or, Desktop as a Service in full.

A general comparison

Let’s start with a comparison first. We all know VDI by now; Virtual Desktop Infrastructure; a desktop-centric service that hosts user desktop environments on remote servers, which are accessed over a network using a remote display protocol (RDP / ICA). A connection brokering service (a Remote Desktop Connection Broker or a XenDesktop Delivery Controller for example) is used to connect users to their assigned desktop sessions. It’s often confused with Remote Desktop Services (RDS), or Terminal Services, which might be better known by some, but there’s a distinct difference.

In short, VDI focusses on delivering a virtual machine based on a client operating system on a one to one basis, one VM per user. RDS on the other hand, offers a full desktop experience running on a single shared server operating system, one desktop shared by multiple users at the same time, also referred to as a Hosted Shared Desktop solution. So again, with VDI you’ll get your own client OS based virtual machine (Server VDI is also possible, will be discussed in one of my future articles) where RDS can either offer a (hosted) shared desktop or access to individual applications instead, meaning one application can be used by multiple users at the same time, just as with the (hosted) desktop solution, all made possible by the underlying RDS / Terminals Services technology. Both technologies are often implemented with Citrix software installed on top of RDS, like; Citrix XenApp or XenDesktop (7).

Now for DaaS

DaaS is somewhere in between. It’s basically a VDI solution offered as a cloud service. In most cases the DaaS provider, hosting your desktops somewhere in the cloud, will typically take full responsibility for all hosting services and maintenance when it comes to the back-end infrastructure, including persistent and or non-persistent storage, networking, remote access etc… You also won’t need worry about backups, monthly maintenance (think Microsoft patching for example) and or application installs, unless you want to of course. You’ll pay a fixed monthly fee per machine and the prize will vary depending on the type of machine you need. More memory, disk space and or additional vCPU’s will mean the price goes up and vice versa. Here’s an example, price wise, of Amazon’s newly introduced WorkSpaces:

  • Standard – 1 vCPU, 3.75 GB of memory, and 50 GB user storage. $35
  • Standard Plus – 1 vCPU, 3.75 GB of memory, and 50 GB user storage. $50
  • Performance – 2 vCPU, 7.5 GB of memory, and 100 GB user storage. $60
  • Performance Plus – 2 vCPU, 7.5 GB of memory, and 100 GB user storage. $75


Unfortunately DaaS isn’t as straightforward as it may seem. Sure, you pay a monthly fee and you won’t have to worry about a thing, so to speak, but when it comes to the VDI comparison made earlier, there’s a bit more to it, let me try and explain. When we talk about VDI, as discussed earlier, we’re thinking virtual machines (client OS based) on a one to one basis, meaning each user will get it’s own personal VM, right? Never mind if it’s persistent or not. Before we continue, read this: It all comes down to licensing. This is what Microsoft has to say with regards to client operating systems on cloud hosting platforms: Multi-tenant hosting is restricted in the Product Use Rights of Windows Clients, such as Windows 7 or Windows 8. Windows Client Desktops are not available on either Windows Azure or on any other Service Provider such as Amazon or Rackspace. You can read more about the Microsoft Product Use Rights here. No client OS based machines allowed, simple as that!

So how do all those Cloud DaaS hosting providers cope with this? Well… they don’t! Is the short but honest answer. There’s only one way around this (at least til Microsoft changes it licensing structure) and that’s using Microsoft’s server operating system instead, and this is exactly where a lot of the confusion starts. The concept is simple, you run a Windows server OS on your back-end systems and start offering hosted shared desktops, using the well known RDS \ Terminal Services technology, to your customers.

This is one way of doing it, and it’s used a lot! Next you throw in a feature like Desktop Experience and your users will get the look and feel of a Windows 7 desktop. A quote from Microsoft on this: The Desktop Experience feature allows you to install a variety of components and features that are provided in the Windows 7 operating system onto a computer that is running the Windows Server 2008 R2 operating system. After you install Desktop Experience, the Windows 7 components and features, such as Windows Media Player, will appear under All Programs on the Start menu.

The same can be done for Windows Server 2012 as well. Configure it this way and you’re basically good to go. Your users will think that they’re working on a fully featured Windows 7 (or Windows 8 for that matter) machine, while in fact it’s the relatively simple hosted shared desktop principle instead. I’m sure that most users won’t notice, and even if they did, in most cases they simple don’t care, as long as their daily routines don’t get interrupted. Now don’t get me wrong, I’m not saying that this is a bad thing, it’s actually a quite clever to be honest, and cost effective as well. Besides, the technology involved has proven itself over and over again and is one of my personal favorites as well. For IT however, this might be a different story.

Don’t get confused

Don’t be fooled by smart marketing, they make it sound like you’re buying, or leasing a fully functional client OS based desktop on a one on one basis, and although to the untrained eye, it looks like you’re presented with a Windows 7, or whatever desktop, you’re not! Sure, if you read the product pages or license agreements, they’ll tell you it’s actually a Server OS being used, but still. Just make sure that your IT department is involved when you’re considering a solution like this, they’ll know what to look for. I’m mentioning this because there could be some valid reasons why you may need a on a one on one solution instead of a hosted shared one. I’ll list some below, for example:

  • Because your users may need to install their own updates & applications;
  • Your users, for whatever reason, need to able to modify specific system-level settings;
  • Perhaps in some cases (other than the above) administrative privileges are needed;
  • Certain users might need more processing power and memory than others, because of  certain resource intensive applications they might use;
  • Dedicated / persistent storage might be needed.

Although some of the above might be possible on a hosted shared desktop environment as well, it isn’t a best practice and we could easily end up with more trouble than we can handle. Besides that, not all applications behave the way you’d expect if they’re developed with a Client OS in mind but are installed on a Server OS instead. Do you recognize any of the above? Then you’re probably better off by keeping these specific users on-premises since this is the only way we can deploy (legally anyway) client OS based machine to our users. It’s always going to be a mix and match process. Or am I wrong?!

Back to VDI, again

There is a way in which Hosting Providers can offer VDI based DaaS using a server OS, that’s right, on a one on one basis just as with ‘normal’ VDI. I already mentioned Amazon and their WorkSpaces DaaS solution, it’s big news within the ‘community’ and has been for weeks. And to be honest, it’s one of the main reasons why I wrote this article in the first place. I mean, it doesn’t happen every week that one of the largest cloud hosting companies in the world, or perhaps the largest, get’s involved in DaaS computing, it’s trendsetting, in way. It’s not that Amazon is presenting us with something completely new, not at all, it’s just that they’re Amazon, they’re big and they’re known, and that’s what matters.

In the case of Amazon’s WorkSpaces, it’s actually Windows Server 2008 R2 running in the background. I first thought that they applied the hosted shared desktop principle as discussed earlier, but I was wrong (thanks Brian) These are server based desktops offered on a one to one basis, one user per Windows server desktop. DaaS (VDI) based on a Windows server OS including persistent storage! Exactly what the doctor ordered! Unfortunately this model isn’t applied very often, in most cases it isn’t very cost effective to offer DaaS this way, but I guess for Amazon this isn’t that big of an issue. Of course If, for some reason, your applications do have a specific need for a client OS than this won’t work either, but it’s definitely a step in right direction.

Windows Azure

Sort of similar to the above (although meant for a different use-case), a few months ago, Citrix together with Microsoft announced XenDesktop 7 on Azure integration with the following statement: With the introduction of Azure support for Remote Desktop Services Subscriber Access Licenses (RDS SALs) a broad set of opportunities to leverage Azure for hosted Windows desktops and applications begin to unfold. As a platform Microsoft Azure provides a robust, state of the art infrastructure and global presence for enterprises and service providers. Followed by: Citrix customers wanting to leverage public cloud infrastructure as a service in order to expand their on premise datacenter capabilities, without investing in new capital resources, can now host virtual desktops based on XenDesktop 7 within Azure.

Again making it sound like a client desktop OS solution, but it’s clearly not. In this case it’s actually the Hosted Shared Desktop model being offered, with the single user server solution only used if there’s no other way. Have a look here I wrote an extensive article on the subject. About a week later I had a good conversation with Citrix’s Kurt Moody regarding the matter, a few days later I wrote this it’s all water under the bridge now. My point is, it’s very easy to get mislead, or at least confused by marketing statements like these.

Although the XenDesktop 7 on Azure design is meant as an on-premises extension for companies looking to expand their existing datacenter without having to invest in new hardware (of course that’s not the only advantage), the concept isn’t that different when you think about it. It’s still about hosting your desktops in the cloud one way or the other. With Amazon’s WorkSpaces however, it’s all simplified, you don’t need to install and or configure anything, no maintenance, management or backups etc… You just pick what you need, adjust as (and if) needed and you’re done. Also, you won’t have to make any upfront investments either, you just pay per use, so to speak, although this applies to Azure as well as mentioned above. Amazon will take care of the rest.


Solutions like Amazon’s WorkSpaces aren’t for everyone, I can imagine that small(er) and mid sized companies, ranging from 50 to several hundreds of users might be interested. Although you’re presented with multiple configurations to choose from, you’re still bound to what Amazon has to offer, this goes for management as well and could be a drawback for some. For example, if it’s Server 2012 that you want, at least for now, you’re out of luck. Note that you are able to install your own software (by IT) and you can use the licenses (your own) that go with it. Also, all other changes made by your users are persistent as well. See this Blog from Brian Madden on some of the features and possibilities that they offer, he asked them 50 questions and got 50 answers.

Although with Azure you’ll still need to build up, configure and manage the whole infrastructure yourself (this can be an advantage as well and you won’t have to invest in any hardware upfront) you do have the option to go with Windows Server 2012, or 2012 R2 even, if that’s what you need. A small advantage perhaps, I  guess it all depends on the use case you’re presented with. Simply put, If it’s more flexibility and or manageability that you need then WorkSpaces might not be the right solution for you, have a look at Azure, perhaps use Amazon Web Services in another way or just keep your datacenter on-premises instead and handle your own storage, user profiles, folder redirection and so on.


This should give a good idea on how DaaS solutions work, or perhaps even more specific, how DaaS licensing works. Keep in mind that for now I only briefly discussed Amazon WorkSpaces and Windows Azure, not only are they big, they also offer some specific services which helped in explaining some concepts. Just know that there are (much) more providers out there offering similar solutions, Citrix included of course. Have a look at Nebula as well; it’s DaaS the way it should be, offered by Qwise from the Netherlands! Storage, user profile management and management capabilities in general, which we all haven’t really discussed up till now, will probably differ per provider, although not much, do make sure you know exactly what you’re getting yourself into before taking the leap.

Bas van Kaam ©

Reference material used:,,, and


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