Introduction
Virtualization technologies were initially adopted to address issues like server sprawl, low server utilization, data center footprint size, power/cooling problems, and IT budget reductions. In the last few years, Virtual Desktop Infrastructure (VDI) is an area where interest is beginning to surge and new virtualization solutions are being tested and deployed to solve end-user desktop provisioning and management headaches. In addition, VDI also becomes another means to further reduce IT operating costs.
VDI solutions allow an organization to deploy virtual desktops on server farms hosted in data centers and provide one-to-one user connections to a virtual desktop through a multitude of thin or rich client devices that range from simple terminals to full-fledged desktop or laptop computers. In consequence, virtual desktop computing is performed on the data center servers, while the user interface is presented on the client devices using a remote desktop client application. A VDI is not a single product solution, but rather, consists of a combination of hardware, virtualization software, and management tools to provide an end-to-end solution towards the provision, configuration, and management of virtualized desktops.
Microsoft VDI Solution
Microsoft’s VDI solution shares many components with those used to implement a server virtualization infrastructure. Essentially, the Microsoft VDI solution builds on top of the same server virtualization and management base, adding the specialized components for virtual desktop management. Microsoft, in alliance with Citrix and other partners, provides a set of components that allow you to implement both static and dynamic virtual desktop solutions.
Static Virtual Desktop
A static virtual desktop directly replaces a physical desktop and runs in a persistent virtual machine that is dedicated to a particular user. The user connects directly to the virtual desktop using a remote desktop connection application. A static virtual desktop may consist of a guest operating system and installed applications, or it can make use of Terminal Server, application virtualization, and application streaming for isolation and dynamic delivery of applications.
Dynamic Virtual Desktop
A dynamic virtual desktop is usually provisioned and assembled from a single master image and uses Terminal Server, application virtualization, and application streaming as well as user-specific settings to deliver a personalized but non-persistent virtual desktop to a user. User data storage can be persistent by storing data in a virtual hard disk that is connected when the virtual desktop is initialized and disconnected when the virtual desktop is deactivated.
Microsoft Windows Server 2008 Hyper-V
Microsoft Windows Server 2008 Hyper-V is the virtualization layer component in a Microsoft VDI solution. With hypervisor-based technology, Hyper-V supports concurrent and isolated secure partitions in which you can execute individual virtual desktops. Based on its integration with Windows Server 2008, Hyper-V provides the migration of virtual desktops between Hyper-V servers using built-in failover clustering resulting in minimal downtime. This functionality is also referred to as Quick Migration. With Quick Migration, virtual desktops are placed in a saved state prior to being moved and restarted on another Hyper-V cluster node. This is useful if a Hyper-V server requires planned maintenance or you need to rebalance the Hyper-V virtual machine load. The failover clustering support in Hyper-V also provides the ability to restart virtual desktops on a new Hyper-V cluster node in case of an unplanned event, such as a hardware failure. Because Hyper-V supports a wide array of devices including; SAN, NAS, DAS, and iSCSI, you can choose the optimal configuration to support small- or large-scale VDI deployments. In terms of client connections to virtual desktops, Hyper-V provides access through the remote desktop protocol (RDP).
Windows Vista Enterprise Centralized Desktop
The Windows Vista Enterprise Centralized Desktop (VECD) encompasses the licensing options available to deploy Windows virtual desktops in a VDI environment. VECD defines licensing models for virtual desktops accessed through either traditional desktops or thin clients. Licenses are allocated on a device basis. A traditional desktop license requires an annual subscription in addition to Windows Software Assurance. A thin client license requires only an annual subscription that includes Windows Software Assurance. In either case, you can install an unlimited number of copies of Windows Vista Enterprise or downgrade operating systems, and you can access up to four concurrent running instances from a licensed device. The licenses apply to both static and dynamic virtual desktop architectures. Because licensing options are often complex, you should thoroughly review the VECD licensing options based on your VDI architecture plans. VECD licensing details are available here.
Citrix XenDesktop
If you are interested in deploying a dynamic virtual desktop solution, Microsoft’s partner, Citrix, provides XenDesktop to manage enterprise scale deployments. XenDesktop works with Hyper-V and is composed of several components that operate in tandem to deliver a personalized, on-demand virtual desktop to a user. It is vital to understand that the Desktop Delivery Controller (DDC) is the XenDesktop connection broker that identifies a user and dynamically assembles his/her virtual desktop. After the user is identified, XenDesktop can stream the operating system to the virtualization host environment, apply the user’s profile to the operating system and supply the user’s applications through a policy-based, integrated application delivery technology such as Microsoft Application Virtualization or Windows Terminal Services.
Microsoft Application Virtualization 4.5
Microsoft Application Virtualization 4.5 (App-V) provides server-based components to centralize storage and management of applications, and on-demand, streamed delivery of applications to virtual desktops. In conjunction with the App-V server components, App-V requires a client-based component that creates an isolation environment on the virtual desktop within which an application executes separately from other applications, eliminating concerns about system instability caused by file versions or registry setting conflicts. App-V also provides the ability to stream only the portions of the code that are needed to start an application on the virtual desktop, providing additional portions based on actual user need. App-V can preserve application preferences in a file-based cache on the virtual desktop to speed up subsequent application launches, something that is useful for a static virtual desktop deployment. In a purely dynamic environment, application and user preferences are reapplied each time the dynamic virtual desktop is assembled and delivered to an end user.
Microsoft Windows Server 2008 Terminal Services RemoteApp
Microsoft Windows Server 2008 Terminal Services RemoteApp can also be integrated into a VDI solution to provide virtual desktop users with access to applications without embedding them or executing them on the virtual desktop. In addition, RemoteApp provides a solution to users who need to run applications that are incompatible with their virtual desktop operating system. With RemoteApp, applications are installed and execute remotely on Windows Terminal Services. In order to provide a seamless virtual desktop user experience, a RemoteApp-based application is launched by a user clicking on an icon integrated into the virtual desktop or an entry in the Start menu. The icon is linked to an RDP or MSI package that contains the instructions and parameters to launch an RDP session to a terminal server and invoke the application. When the connection is established, the application runs in a separate resizable window on the virtual desktop, side-by-side with local applications. File extensions are associated with RemoteApp to automatically launch the remote application, ensuring that the user experience is identical to the execution of local programs.
Microsoft System Center Virtual Machine Manager 2008
Microsoft System Center Virtual Machine Manager 2008 (VMM) is the management component that provides you with a single integrated console to manage your physical servers running Hyper-V and the virtual machines that they execute. VMM can provision virtual desktops and use Intelligent Placement to determine the best Hyper-V server to deploy them on based on several characteristics, including Hyper-V server load. Intelligent Placement relies on the integration between VMM and System Center Operations Manager (SCOM), which is the source of performance data collected from deployed Hyper-V servers. VMM also provides built-in functionality to perform a physical-to-virtual (P2V) migration of a disk image, virtual machine library storage and management, and policy-based user self-service provisioning of virtual machines.
Microsoft System Center Data Protection Manager 2007 SP1
System Center Data Protection Manager 2007 SP1 (DPM) is the management component that allows you to support Volume Shadow Copy Services (VSS) backups of active virtual desktop operating systems, provided that they are VSS-aware. For desktop operating systems that are not VSS-aware, DPM allows you to back up virtual desktops offline by shutting down or saving the state of virtual machines and then backing up the file set that constitutes a virtual machine.
If you are interested in more details on how to use DPM 2007 SP1 to back up the Hyper-V server configuration and virtual machines, watch my video titled “Backing up a Hyper-V Host using DPM 2007 SP1” that is posted on the VirtualizationAdmin.com site.
Microsoft VDI in Windows Server 2008 R2 Hyper-V
With the upcoming release of Microsoft Windows Server 2008 R2 Hyper-V, the Microsoft VDI solution gains three important features: Live Migration, Cluster Shared Volumes, and Remote Desktop Connection Broker. Live Migration will support virtual desktop migration between Hyper-V failover cluster nodes with no perceived service interruption for a user. For more details, read my article entitled; “Live Migration in Windows Server 2008 R2 Hyper-V”, posted on the VirtualizationAdmin.com site.
Cluster Shared Volumes (CSV) allows multiple failover cluster nodes to concurrently access a Logical Unit Number (LUN) on a shared storage system while providing a consistent file namespace to all cluster nodes. With CSV, management and storage of a large number of virtual desktop files or Virtual Hard Disks (VHD) becomes a simpler proposition and removes the drive letter limitations that you can encounter in Windows Server 2008 Hyper-V. A VHD is the file format that is used by Hyper-V to encapsulate individual virtual machine operating system, and application data.
In Windows Server 2008 R2, Terminal Services is renamed as Remote Desktop Services. The Remote Desktop Connection Broker takes the Session Broker functionality found in Windows Server 2008 that provides connection to traditional session-based remote desktops and extends it to provide connection to static and dynamic virtual desktops. Although targeted for small-to-medium virtual desktop deployments, the functionality can be used as a platform by Partners to develop larger-scale enterprise solutions.
Conclusion
Virtual Desktop Infrastructure represents a combination of hardware, virtualization software, and management tools that provide an end-to-end solution to provision, configure, and manage virtualized desktops. A VDI solution differs from a terminal services solution by providing each user with a separate, isolated, secure workload (operating system and application stack) instead of an isolated session executing on a single operating system instance. Whether you need to deploy a static or dynamic virtual desktop infrastructure, the components that integrate together to comprise a Microsoft VDI solution include Windows Server 2008 Hyper-V, VECD, System Center VMM 2008, System Center DPM 2007 SP1, Windows Server 2008 Terminal Services, Microsoft Application Virtualization 4.5, and Citrix XenDesktop.
