My take on VDI.

In the past year if I could get a penny everytime I heard the word VDI I would not be here writing this post anymore. In the Server Based Computing/Virtualization industry, Virtual Desktop Infrastructure (VDI) is “the” topic and as mentioned, has been like that for a while.

Some people in the industry (mostly the Microsoft MVPs for RDS – the new name for Terminal Services) do know what I think but as not everyone is part of that group, here you have my take on this:

1. I am not sure why people like Brian and others do not compare VDI to real desktops. In a typical VDI scenario virtual machines running a desktop OS like Windows XP or Windows Vista are accessed by users using some sort of protocol (RDP, ICA, etc). For example Citrix XenDesktop uses ICA and Provision Networks/Quest uses RDP. But today, with client hypervisors (a local hypervisor installed on your PC) you can run all these virtual machines directly on your own PC and not on a remote server. So VDI in a way is evolving. In the future I do see users using their VMs over ICA/RDP when at work and when disconnected, using them locally through a local hypervisor. Get back to the office and all changes are replicated. Cool.

If we think about how many companies simply skipped the whole Server Based Computing thing, that never ran any application or desktop off a centralized TS/Citrix farm and how many companies are just now taking off the ground I do think it is simply natural their IT guys willing to compare how a VDI solution compares to a full blown desktop (real desktops/fat clients – whatever name you want) approach. Especially now that local hypervisors can be seen in the wild.

Again, these companies simply missed the SBC bandwagon. Like several companies I know that never deployed Windows 2000. Jumped straight from NT 4.0 Domains to Windows Server 2003 Active Directory. For them, whatever Microsoft introduced or did with Windows 2000 was completely irrelevant. The same applies here. These companies never cared about SBC/TS/Citrix. They are/were a full blown PC/Desktop shop. Now that virtualization is becoming widespread they simply want to know how a regular PC environment compares to a virtualized one. Dead simple. And I can totally see and understand their reasons.

2. So far, there is always some performance hit associated with VDI. The problem here is simple. If you are trying today to deploy a VDI solution for running Windows 2000 or XP, with a 4-7 years old application, chances are scalability will not be that bad (meaning you will be able to squeeze quite a lot of users in one big server, reducing the cost per user at the end). But if you are always trying to keep up with technology and if your company always goes for the latest and greatest, this means you may be going down the road with Windows 7 with Office 2009 sometime soon. And probably your applications will be written relying on the .NET Framework 4.0. Yes, I do know these are not out today. But keep in mind that with cheap hardware comes lazy programmers and huge frameworks. Long gone are the days when we had to squeeze as much performance as we could out of a DOS app because an extra 1MB of RAM on each PC would break the company.

I cannot see .NET ZZ getting leaner or faster; same for Office 20XX, Windows YY (replace X, Y and Z with any integer). They may look faster but that is the result of much faster hardware with much more memory. That is why I came up with the ‘Claudio’s Law’ like in the ‘Moore’s Law’ (that old dude from Intel): “The time it takes for Windows XXX to boot and load Office YYY on its current generation hardware is constant” and you can try that for yourself. Get an old PC (PII 266MHz with 64MB RAM) with Windows 98 and try loading Office 97. Now fast forward to today and get a typical machine running Windows Vista with Office 2007 and do the same. The time it takes to load is virtually the same!

Where do I want to go with all this? If you keep running the latest and greatest I cannot see VDI being a scalable solution. It is a solution for sure but if scalability is not there it means a much higher cost per user as you cannot run hundreds of VMs in a single box. Plus if you want to do it properly, you will not be hosting 100s of users on cheap hardware. You will go for the good stuff. And good stuff comes at a price. An 8-CPU box with 32 cores and 64GB RAM, RAID and fast hard disks does not come cheap. And now, in a recession, I am 100% sure costs will decide the fate of several IT initiatives out there. The bottom line in many places will be indeed this: money.

Unless Microsoft/Intel/God comes up with a new way of doing things that will allow us to run 100 VMs on the above hardware, all running the latest and greatest OS and apps, I cannot see this changing.

3. Local Hypervisor. Ok this adds quite a bit to the picture as now you can run the VM directly on your PC, without sharing resources with anyone else. Sounds great, doesn’t it? The problem here is there are several OS enhancements that are now dependant on the hardware. For example, Snow Leopard and Windows 7 are now offloading certain tasks to the GPU. Several other components on the OS rely on that low level direct access to the hardware. When a hypervisor layer is present, as of today, several of these enhancements are lost. This means a performance hit. Of course there are several benefits with that approach (i.e. your ‘master images’ become hardware independent, running pretty much anywhere, as long as the hypervisor is there) but in an age where users can go to Best Buy and get a decent, fast PC for under $600, are they willing to work on something that is slower (potentially much slower depending how OSs evolve) than what they have at home? If hardware manufacturers start implementing changes that will allow things like a virtual GPU and so on that will probably be minimized/eliminated and VDI may take off.

But then we may break the whole cycle of software/hardware Wintel upgrades and the industry behind that. Companies like Dell, HP, Lenovo, etc do rely on users and companies buying and replacing computers every couple years. So at the end, what impact such approach will have in the industry? I do know we, human beings, always adapt and I am sure these companies would have to adapt to survive the new way of doing things.

Well that is what I think. As you can see I do not think VDI is bad, ugly, beautiful or great. I do think it has its own merits, it is capable of solving problems other approaches may not work well and it is still in its infancy. But I cannot simply see how all its drawbacks/issues/costs will be addressed by 2010. Sorry Brian.


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