How many resources should I allocate to Windows XP virtual desktops? What about Windows 7?  This is a big question as it helps define how many servers you will need and how much money your desktop virtualization solution will eventually cost.  I’ve seen some widely ranging specification for these answers and I wanted to provide you with what some of our consultants recommend (myself, Nicholas Rintalan, Doug Demskis and Dan Allen). These are reasonable estimations for resource allocation for Windows 7 and Windows XP desktops when delivered in the hosted VM-Based virtual desktop model (or VDI for short). To put it another way, this is what we are seeing.

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
Normal Windows XP 1 1-1.5 GB 6-10 8-10
Windows 7 1 1.5-2 GB 8-12 6-8
Power Windows XP 1 1.5-2 GB 12-16 6-8
Windows 7 1-2 2-3 GB 15-25 4-6
Heavy Windows XP 1 2 GB 20-40 4-6
Windows 7 2 4 GB 25-50 2-4

See anything shocking? How about the potential of 1.5 GB of RAM for light Windows 7 users? Remember, we are talking about the typical implementation that we have seen. That means the desktop image includes antivirus agents, malware agents, monitoring agents and line-of-business applications.

These agents and applications add up (especially Line-of-Business apps). Even though the user is a light user, that means they only run 1 or 2 applications. However, those applications are more than Microsoft Word. They are the main Line of Business application. So even though they don’t hit the CPU hard, they still consume a lot RAM (of course these implementations could just put the line of business app on XenApp and not worry about providing a true Windows 7 desktop for light users, but that is a discussion for later).

Of course context is everything and how you define the four groups of users plays a big role in how you allocate resources.  Here is how we define them:

Group Description
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.

I’m hopeful that as you start planning your XenDesktop environment, you use realistic approximations on your virtual desktop specifications.

If you want to know more about resource allocation as well as many other areas for planning a XenDesktop environment, then sign up for the XenDesktop Design Handbook. This helps guarantee that you have the latest and greatest design information available.

Daniel – Lead Architect – Worldwide Consulting Solutions
Twitter: @djfeller
Blog: Virtualize My Desktop
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