I recently posted a blog focusing on the resource requirements for hosted VM-based virtual desktops. These are realistic numbers and should make you wonder if the hosted VM-based virtual desktop is the most appropriate solution for all four user categories. What I found interesting was I had another blog identified as a follow-up talking about if the hosted VM-based desktop model made sense for all of the defined user groups when I started to receive emails, blog comments and twitter comments expressing the same concerns. This is great! That means many more people realizing that desktop virtualization does not always mean the hosted VM-based desktop model.
Let me explain further. As a refresher, we typically break down users into one of four groups defined as follows:
|Light||One or two applications no browser-based activity|
|Normal||Multiple applications with limited browser-based activity|
|Power||Many simultaneous applications with extensive browser-based activity and Internet-based applications.|
|Heavy||Few applications but have heavy system resource requirements. Data processing, compiling, or graphics manipulation are common applications.|
Of course as you move up the levels so too do the requirements for the hosted VM-based virtual desktop. But does it really make sense to have our light users running on the hosted VM-based desktop model? For light users, we typically define the following in terms of resource allocation:
|User Group||Operating System||vCPU Allocation||Memory Allocation||Avg IOPS (Steady State)||Estimate Users/Core|
|Light||Windows XP||1||768MB-1 GB||3-5||10-12|
|Windows 7||1||1-1.5 GB||4-6||8-10|
Is this crazy? Why does a user who only runs 1 or 2 applications, which are most likely line-of-business applications, require a hosted vm-based desktop environment? If you then go back to our high-level recommendations on application integration, you will see that many line-of-business applications are better served as applications virtualized on XenApp. This isn’t because desktops can’t run the applications; it is because many line-of-business applications are complex, have many dependencies, require extensive configurations. Hosting these applications on XenApp is something that has been successful for years and virtual desktops do not change that fact.
Many of the issues we’ve seen with organizations running hosted shared desktops in the past is that it doesn’t look or feel like the desktop OS. That was then, this is now. Windows 2008 can look like Windows 7. Challenge solved.
Many organizations struggle to justify transforming their desktop environment due to the costs associated. I agree, there is a cost, but the cost can be significantly reduced if you don’t go in blindly. If we use the hosted shared desktop model for our light user loads, we can save. Think about it this way, every light user will need 1-1.5GB of RAM for their hosted VM-based desktop session. Of that amount roughly 768MB of that will be just for the OS. Why does each one of the users require a full-fledged desktop OS? If we share the desktop across 100 users, we save almost 8GB of RAM. It doesn’t sound like much but what about 1000 users or more? And we haven’t even begun to discuss the impact on storage for these users.
So far we are only looking at the OS requirements; what about the application RAM requirements? Because the resources are completely shared, if the application requires 200MB to run, a large percentage of that amount can be shared across all users, helping to reduce the overall RAM requirements (and many Line-of-business applications I’ve seen, including the dependencies, need way more than 200MB of RAM).
So what is my point in all of this? Just because you are looking at virtual desktops, it doesn’t mean that you must put all of your users onto the same type of virtual desktop. Align the technology you implement with the user requirements.
Daniel – Lead Architect