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Understanding more about Desktop Virtualisation–VDI and RHSD and how to pick between them

I am frequently asked questions about Microsoft, what our VDI, DV or RHSD solution looks like and how to license it as I look after the relationship between Citrix and Microsoft in the UK.  Having seen the article at Computer Weekly I decided I would share some thoughts on what it is and how to license it (licensing in a blog later in the week). 

On the licensing front, I should say, while I have a lots of experience, always talk to a Microsoft Licensing Specialist. Always!  Microsoft licensing moves forward to enable more customer scenarios all the time, so by the time I hit send, it could be out of date already.  Sad but true.  To quote from the article above, which is very good (except for the licensing sidebar which is confusing IMHO)

“But one research firm that has looked at Microsoft’s new EA, has found that Microsoft has, in fact, simplified client access licensing. “

What is DV, VDI and RHSD

First off, I’m assuming everyone is clear on the difference between DV and VDI.  Ok, maybe not, so my 30-second guide:

  • DV (for me) is the use of a Windows Server to serve out desktops or applications from a single Windows Server operating system or the use of VDI or the use of a type 1 or type 2 hypervisor on the desktop to give us a 2nd operating system that we can access applications from.  It is bigger than VDI and to be honest, most of the time when people talk to me about VDI, they mean RHSD.
  • RHSD (Remote Hosted Shared Desktops or Remote Desktop Services/Terminal Services) is the use of a Windows Server to serve out desktops or applications from a single Windows Server operating system .  Each user see’s the same applications and has no-admin rights
  • VDI is the use of Windows (probably Windows 7 today) served out from a virtual machine running Windows 7 guests (obviously on Hyper-V server as the host for the best performance Winking smile)

RHSD has been around for years – Terminal Services, Remote Desktop Services are the Microsoft name and Citrix has been offering a solution by many names for years too.

VDI has been around for a little while, however most people who have tried moving to it have discovered that the skills required to deliver a server VM are very different to those required to deliver a desktop.  This means you have to re-evaluate your hypervisor, network and client devices completely separately from your current thinking around server virtualisation.  Some reasons include:

  1. Users expect a different level of UI responsiveness compared to server users
  2. the IO requirements are different (as you may have 100 VMs on the one box, not 3-10)
  3. minor slow-downs that a server might experience are not acceptable to the user of a PC who has had it replaced by something remote
  4. A client device is always connected to the VM and it needs to be up to the task (anyone want to use Lync, VoIP, Skype…, watch video etc etc)
  5. The network requirements always go outside the datacenter to client networks that may be outside the businesses control

So, we have the concepts – desktops (or apps) are delivered from a central pool, in the datacenter instead of on the end-user device.  It goes without saying that in these scenarios there is a requirement for connectivity for people to work.  The upside, most devices can support the client presentation software, so giving more flexibility here.  I’m sure someone will tell me that there are also solutions that can be disconnected – yes, but I’ve not seen anything yet that scales and is something I would want to roll out to my customers, friends or even tinker with for more than a few minutes.

It is also worth saying that moving to a DV solution does not solve any desktop management issues at all, it adds to them, however in a transition, new management can be put in place that significantly simplifies desktop management and opens up the ability to offer employees new services and working lifestyle choices.  Of note though is that these management changes can be delivered with or without having to touch any DV options today (e.g. Windows Intune, System Center)

My definition of DV is still not complete (it is a very broad area) and I’m trying to focus on the licensing associated with VDI and RHDS, so you may find it very useful to see a broader look at information at the Windows Server web site and at Ian's blog for much more information.

How to choose

I’m working on the assumption that you have already chosen to go down the DV route, so you understand the requirements, benefits and costs of moving this way.  if not, get a partner who knows lots about DV to help you and make sure they can offer anything from 100% physical to 100% virtual solutions. Why, well if they don’t I would assume their skills are not broad enough and this means that you are less likely, although not always, to hear a sales pitch that is 100% covered by the services they offer.  If they don’t offer physical desktop and virtual services, they are unlikely to give you unbiased advice.  The advice may still be to go to a 100% DV solution, but I’ve seen some promise the earth delivered virtually as it is all they have to offer and then problems happen.  I may be teaching my grandmother to suck eggs here, but if not, hopefully some sage advice.

So, we want to do some form of RHSD or VDI, which is the right answer?  Well, there are many ways to slice this, but these two graphics about summarise it for me

VDI or RHSD - 1

VDI or RHSD - 2

I will follow this up with an item on licensing in the next couple of day.




Posted Wed, Jan 4 2012 12:15 AM by David Overton


David Overton's Blog wrote VDI and great video performance using RemoteFX (and licensing it)
on Sat, Jan 7 2012 3:11 PM

Having written a little about VDI and RHSD the other day, I see that Register has an item about RemoteFX

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