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Where our team of guest writers discuss what they think about the current trends and issues.

Andrew McGrath
Commercial Dir., Virgin Media Business

How will consumer IT impact your business?

Back in 2005, the analyst house Gartner predicted that consumer technology would have a huge impact on enterprise IT over the next 10 years.
12 May 2010

Desktop virtualization - one size does not fit all

Quest Software | http://www.quest.com

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P eople who ask me when desktop virtualisation is going to explode get the answer, “1997″! That was when I first started setting up Insignia Solutions’ NTRIGUE (an OEM of Citrix WinFrame) and deploying remote Windows desktops and applications on to all manner of devices. In Europe, we just could not install it fast enough – Citrix went from under $50M in revenue to $127M in 12 months. Citrix acquired us in January, and doubled revenues again the next year. Now, with VDI, VMware has caught desktop virtualization fever. Everyone is talking about desktop virtualization more than ever before, and we are poised for the next wave. These are exciting times, but….

One Size Does Not Fit All

It has never been clearer that " one size does not fit all " in desktop virtualization. I have come to this conclusion after interviewing our most savvy prospects and customers, who are currently analyzing their user populations to figure out which type of desktop deployment is appropriate for each class of user. Their objective is to find the most cost-effective solution that meets their needs. In a perfect world, we would all standardise on one desktop deployment method, but this is not going to happen anytime soon, for two reasons:

  1. Some desktop virtualization technologies can cost two to four times more than others
  2. An increasing percentage of users use laptops and notebooks and need a functional working environment when they are offline. The deployment techniques that slash management costs for task and desk workers require that the remote users stay connected, so another approach is needed.

Hosting or virtualising a Windows desktop in a virtual machine (VM) - also known as VDI, HVD and others - has many benefits.  Unfortunately, this is typically the highest cost desktop virtualisation technology, especially if you use a NAS/SAN file storage device shared across multiple VM hosts. Before you spend vast sums of money on a VDI project to cover all of your users, be sure to consider the alternatives. Some of the following also work for offline users:

  • Smarter management of your physical desktops
    There will always be a set of users with "rich clients," either desktops or laptops, so virtualising desktops will not be a panacea. You're going to have to develop a management strategy for physical desktops as well as virtual ones.
  • VDI using storage on the VM host itself ("local storage")
    OK, it's subset of VDI and not really an alternative, but it is a great way to reduce costs, especially if you are not using persistent (or "personal") desktops, and have no need for VMotion or live migration of VMs. Distribution of hard disk images is an overhead, but you will still face that problem  when you use linked clones or differencing disks.  You can typically only link 50-100 children from each parent disk image.
  • Terminal Server (TS), or Remote Desktop Session Host in its Windows Server 2008 R2 guise
    TS may be the forgotten man in all of this VDI hype, but it is two to four times cheaper than VDI. Yes, there are more application incompatibilities - many of which can be solved, but not all. it's not a true "desktop" (although most users cannot tell the difference), and it takes more skill to manage. But:

    • VDI is increasingly focused not on persistent desktops that are permanently assigned to one user; it is used more often for a pool of non-persistent desktops created on the fly and prepared for the user with app streaming. There are many reasons for using this approach, but the chief reason seems to be that VMware doesn't make any money from Terminal Server, so a lot of prospective VDI customers never hear about it!
    • Citrix's financial reports show that the large majority of their new license revenue still comes from Terminal Server.  It's a little fuzzy because XenDesktop Enterprise and Platinum include XenApp, their TS product. They have an attractive trade-in program to convert existing XenApp customers to XenDesktop, even if those customers have no near-term plans to explore VDI. Despite that, more than 90 percent of the revenue is created by Terminal Server.
      3) Madden's Paradox . This article by the legendary Brian Madden describes his confusion over the large sums of money that people will spend on VDI when a TS solution would deliver the same benefits at a fraction of the cost.
  • Application Virtualisation
    Application virtualisation is very effective if the primary problem in your desktop estate is actually application management and updates. Not all apps can be virtualised, and different app virtualisation vendors have different coverage, but this is a proven technology that is growing in popularity. App virtualization/streaming is also very helpful in VDI/Terminal Server environments for making them easier to manage and reducing management costs even further, especially with Microsoft delivering 64-bit support in App-V 4.6.
  • Client-side VMs, with a type 1 or type 2 hypervisor
    Client-side hypervisors, and the type 1 vs. type 2 debate is about to escalate another notch as Citrix and VMware sharpen their knives. The rationale is that physical desktops would be a lot less hassle if they had a protected, centrally-managed workspace that the user could not penetrate. Type 1 promises better performance, but it is a difficult and new technology, and usually requires a computer be rebuilt. Type 2 has been in use for years and can run on any existing computer with sufficient power, but has some performance limitations. And questions remain about recovery, and how/if to sync offline VMs with those in the datacenter.
  • Parallels Virtuozzo Containers (PVC)
    Parallels is better known for type 2 hypervisors in the consumer space, especially for running PC apps on a Mac. However, they also have a really innovative solution for virtualising desktops on Windows Server 2003 and providing an environment which looks and feels like an XP desktop to the user. With Windows Server 2008 R2 support now in release candidate, they will be able to do the same for Windows 7. The technology is similar to the user density of Terminal Server with the session isolation of VDI. In other words, application compatibility is generally better than Terminal Server (although anything that uses drivers needs to be "whitelisted" by Parallels) but the cost per-desktop is way lower than VDI. At Quest we have a 6000-user case study ( Donna ISD ) running on PVC.

The best desktop virtualization plans use a combination of all of the above to achieve the lowest average cost per user. Quest vWorkspace provides a management layer that pulls all of these pieces together in one console, and automates and simplifies the processes required to create, configure and access virtual apps and desktops.


Jon Rolls is vice president of product management for the Quest Desktop Virtualization Group. Jon joined the Quest family in 2004, and brings 15 years of software industry and Windows management experience, including product management roles with Citrix, ScriptLogic, and virtualization and web acceleration startups.

Jon has a Bachelor of Science degree in pure mathematics from the University of Warwick, England.

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