Tech: When VDI is better than Terminal Services approach

In the last months Virtual Desktop Infrastructure (VDI) approach (as VMware use to call it, hosted virtual desktops elsewhere) got a lot of traction, with notable vendors like Sun jumping in the market along with new startups (Qumranet is the last one in the timeline).

Along with vendors, some customers start to consider VDI approaches as valuable alternatives to well-known terminal services approaches.

Dave Caddick, Enterprise Architect at Neoware (now acquired by HP), describes an interesting scenario where VDI seems better:

Greenfield Design Criteria for 5,000 Users:

  • 60% Task based workers suitable for Thin Clients = 3000
  • 30% Knowledge Workers suitable for VDI = 1500
  • 5% Developers or similar suitable for PC’s = 250
  • 5% Mobile Workers with Laptops = 250

Of the mobile workers with Laptops I would think that 60% (or more) of these could be provided with Mobile Thin Clients

60% of 250 = 150 with Mobile Thin Clients and 40% of 250 = 100 with traditional Laptops


So on initial inspection we would appear to have:

  • VDI = USD 400 per user (exc. costs of Desktop License)
  • Citrix = USD 562 per user (exc. costs of TSCAL)

And to me this looks like it’s quite favourable to Citrix, when you add the cost of the Desktop License then the advantages of a Citrix deployment with it’s ease of use, readily available skills, mature product set and features, it’s almost a no-brainer?

However, as discussed above, if you change the figures to reflect that you can only achieve a max. of 40 users per server then it starts to tip the other way. Now we have a 17K server and 14K of Citrix Licensing only supporting 40 Users and the server cost per user now becomes USD 775.

Although VDI is currently “in vouge” I would have not thought that VDI can match the “Bang for the Buck” that can be achieved by Terminal Server/Citrix Installations, however I am now thinking that it’s quite likely that other people’s numbers won’t neccessarily be the same as mine and this could be based on a wide number of factors. So this then may be very influential in peoples perceptions and may well have an impact on what the numbers are calculated to be in ROI’s and TCO’s before commencing a project…

And even Brian Madden, well-known terminal services expert, is reporting a scenario where VDI was a better solution:

Let’s start at the very beginning. Gabe and I worked with this university six months ago. They were not using any server-based computing or streaming or anything like that. It was a brand new environment. They had four scenarios (or “use cases”) they wanted to enable:

  1. There are 1200 lab workstations throughout campus. Users need to be able to walk up to any one of them and access any of 200 applications. The users also need access to their own data and profiles.
  2. They want to publish a remote desktop via server-based computing to people so that they can access the “lab workstation” from their dorm rooms or off campus.
  3. They want to publish individual applications (as opposed to a full desktop like in Scenario 2) to users on their own computers.
  4. Longer term, they want people to be able to run these applications locally on non-university-controlled workstations (i.e. student laptops), and they want this to work offline.

Why no Citrix? (Well, other than Ardence, which is now owned by Citrix.) The problem with Citrix in the server-based computing market is that their desktop server product is a completely separate product from Presentation Server. Even when Desktop Server version 2 comes out, it’s still a separate farm, a separate database, and additional licensing on top of the $500 per user or whatever Presentation Server costs these days.

Provision comes in with their single product at something like $100 per user which supports Terminal Server-based and VDI-based SBC models in the same product, and it also provides the seamless application publishing from Windows XP VMs which is perfect in this case and not even on Citrix’s roadmap. So Provision is a no-brainer.

As for using VDI instead of Terminal Server for the published desktops and applications, this means the university gets broad application compatibility and can use the same desktop images everywhere, and it only costs them USD $6,000 per 50 concurrent users instead of $3,000. Really that’s not too bad from a capital cost standpoint when compared to the fact that they have a much easier time managing the thing and they don’t have to figure out local solutions and more servers for non TS-compatible apps…