VDI vs. RDS, What's the Difference?

Rob Waggoner

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Customers often come to us asking for VDI, but after understanding what they are truly looking for, they understand how RDS can meet their needs and save moneyLet’s talk about the difference and why one vs. the other may be beneficial to you. 

What is VDI? What is RDS? 
VDI stands for Virtual Desktop Infrastructure and RDS stands for Remote Desktop Session Hosts. What this really means is VDI is built around the Windows Client Operating System, Windows 10. RDS is built around the Windows Server Operating System. At this point you are thinking, of course I want my users on Windows 10, not Windows Server. Right? Well, maybe not.  

Keep in mind that Windows 10 only supports one user per Operating System instance. This means if you need to support 4 users, you need 4 instances, or virtual machines, running Windows 10. In a Cloud environment, that means you need 4 separate virtual machines. From a cost perspective, that means you must pay the runtime cost of 4 virtual machines and the Windows 10 licensing cost for 4 Windows 10 instances. Below is the cost breakdown for 4 users. 

Pricing for the D2_v3 VM in East US  



 Hourly cost  

 24/7 monthly cost  

 VM runtime Cost to support 4 users  


VM without OS license

 $ 0.096  

 $ 70.08  

 $ 280.32  


VM with Windows Server with license

 $ 0.188  

 $ 137.24  

 $ 137.24

This is a basic price breakdown for 4 users. Keep in mind it is not complete because it does not include the Windows 10 client licensing. This chart compares the Azure VM runtime cost of running the 4 VMs required to support 4 users with Windows 10, compared to the single VM running the Windows Server OS. The VM runtime cost includes the Windows Server 2016 license. You just need to add your RDS CALs, or RDS SALs for each user. For Windows 10 licensing, see below. 

With RDS and Windows Server, one instance of Windows Server 2016 can support as many simultaneous users as the und
erlying hardware will support. For a moderately priced Azure VM, we have found that one instance of Windows Server 2016 can usually support four to eight simultaneous users. This means that one single Windows Server license and one single Azure virtual machine can now support your four users at a lower cost than Windows 10. Of course, you can make the virtual machine larger to support additional users, but we do not advocate continuing to make the VM larger, that can get expensive quickly.  We prefer having multiple VMs, each one supporting between 4 and 8 users. The MyCloudIT platform supports auto-scaling so those additional VMs can be started as user demand increases, then after hours, the VMs can be taken offline as users log off. We have a great article talking about how you can keep each VM smaller while using auto-scaling to increase capacity as users log in.   

What's the Difference? 
The two big differences between VDI and RDS really comes down to reducing cost and how you acquire your Windows 10 license. With Azure, your runtime cost includes the Windows Server license and user CALs, you just need to add the RDS SALs for each RDS user. The same cannot be said for Windows 10 licenses. Microsoft is releasing new Windows 10 licensing mechanisms, but I have not seen a complete solution for running Windows 10 in Azure in a VDI environment.  

From a technical perspective, Windows 10 client OS’ managed by the Windows Server infrastructure requires the ability to be able to create new virtual machines on demand. For every VDI scenario I have seen, that means the Windows Server infrastructure will require access to the Hypervisor host. Azure does not expose the Hypervisor hosts to external management, so the only way I can see running VDI in Azure is with nested virtualization. That means that whether you have 1 or 100 users connected, you must always have an Azure nested virtual infrastructure that can support all 100 users running all the time. To me, this limits your ability to manage runtime costs if you are using VDI. Again, when using the Windows Server 2016 OS, VMs can easily be started and stopped directly in Azure. 

Will It Get Easier?  
I believe that using Windows 10 in Azure will be easier over time, but for now, using Windows Server 2016 and RDS will provide the capabilities your users need, while providing a cost-effective solution.  

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