When working with virtual desktops, as with virtual servers, make sure each user's desktop has the appropriate license. Microsoft offers enterprises working with Windows a break with the release of the Windows Vista Enterprise Centralized Desktop license.
The license, which relies on the Enterprise Edition of Windows Vista, requires an Enterprise Licensing Agreement with Microsoft. The Vista Enterprise Centralized Desktop (VECD) license provides unique licenses that allow you to run virtualized desktops -- locally and centrally. VECD also includes the following features:
- Unlimited installs of Windows Vista Enterprise are available or a downgraded desktop operating system (OS) on a server.
- Access devices can license virtual desktops. One license is consumed each time a user accesses a virtual desktop from any device. Remote access from a home computer to the centralized desktop virtual machine is free if the user is the principle user of a licensed device at the office.
- Each user can have up to four virtual instances running on the same access device at one time. However, users cannot use two access devices to connect to these four sessions. Each access device requires one license.
- Organizations can run either static or dynamically hosted desktop architectures. Static desktops assign a specific virtual machine (VM) to a user. Dynamic desktops are generated on the fly to meet users' needs.
- Virtual desktops can run on Microsoft or non-Microsoft infrastructures. For example:
- If you use Citrix XenDesktop, you can host desktop VMs on Citrix XenServer, VMware ESX Server or Microsoft Windows Server 2008 with Hyper-V.
- If you run either VMware's or Microsoft's Citrix-based virtual desktop infrastructure (VDI), you can host desktop VMs on their respective server virtualization platforms.
Obtaining an Enterprise Agreement with Microsoft also gives you access to Microsoft's Software Assurance program. The biggest benefit of this program is the Microsoft Desktop Optimization Pack (MDOP), which can be obtained for an additional $9 per desktop.
MDOP includes several tools specifically designed to support organizations running Windows desktops. The following features are at the core of the MDOP package:
- Microsoft Application Virtualization
- Microsoft Enterprise Desktop Virtualization
- Advanced Group Policy Management
- Asset Inventory Service
- The Diagnostics and Recovery Toolset
- Desktop Error Monitoring
If you're running non-Windows desktops, work with the vendor to ensure that you have the appropriate licensing for each user and each instance of the desktops you plan to virtualize.
Using virtual desktops can reduce the licenses an organization needs to set up its desktops since users only run VMs when they need them. In addition, VECD is licensed on a per access device basis, so you can use it creatively to reduce your Windows desktop licensing costs. When you control the access devices, you can control the number of virtual desktop licenses you need.
Licensing software can be expensive; controlling license requirements by understanding actual usage is the best model in a VDI environment.
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Danielle Ruest and Nelson Ruest
Danielle Ruest and Nelson Ruest are IT professionals focusing on virtualization and continuous service delivery. They are authors of multiple books, including Virtualization, A Beginner's Guide which covers all aspects of virtualization in datacenters of any size, and Windows Server 2008: The Complete Reference which is focused on building virtual workloads with this new OS. They are currently writing a training guide for Microsoft Exam 70-652: Configuring Windows Server Virtualization with Hyper-V for MS-Press. Feel free to contact them at infos@reso-net.com for any comments or suggestions.
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