Desktop virtualization

'Desktop virtualization' is an umbrella term that describes software technologies that improve portability, manageability and compatibility of a personal computer's desktop environment by separating part or all of the desktop environment and associated applications from the physical client device that is used to access it. Desktop virtualization is frequently used in conjunction with application virtualization and (Windows) user profile management systems to provide a comprehensive desktop environment management system.

System Architectures

Desktop virtualization implementations are classified based on where the virtual desktop runs and whether or not the virtual desktop persists between sessions. ^[1]. Software products that deliver desktop virtualization solutions can combine these two implementation methods into a single product to provide the most appropriate implementation to support specific requirements. Neither approach explicitly requires the use of a hypervisor; however, in practice most desktop virtualization implementations do incorporate a hypervisor component.

Remote desktop virtualization

Remote desktop virtualization implementations operate as client/server computing environments. Application execution takes place on a remote operating system which is linked to the local client device where the user interacts with the application. All applications and data used remain on the remote system with only display, keyboard, and mouse information communicated with the local client device which may be a conventional PC/laptop, a thin client device, a tablet, or even a smartphone. A common implementation of this approach is to host multiple desktop operating system instances on a server hardware platform running a hypervisor. This is generally referred to as "Virtual Desktop Infrastructure" or "VDI". It should be noted that VDI is often used incorrectly to refer to any desktop virtualization implementation^[2].

Remote desktop virtualization is frequently used in the following scenarios:

In distributed environments with high availability requirements and where desk-side technical support is not readily available, such as branch office and retail environments.
In environments where high network latency degrades the performance of conventional client/server applications
In environments where remote access and data security requirements create conflicting requirements that can be addressed by retaining all (application) data within the data center with only display, keyboard, and mouse information communicated with the remote client.

It is also used as a means of providing access to Windows applications on non-Windows endpoints including tablets, smart phones and non-Windows-based desktop PCs and laptops.

An extension of this approach can be seen with Desktop-as-a-Service (DaaS), where desktop computing services are offered by a specialist service provider. The DaaS provider typically takes full responsibility for hosting and maintaining the infrastructure, applications and software licenses needed to provide the desktop service in return for a fixed monthly fee.

Remote desktop virtualization is also used as a means of resource sharing, to provide low-cost desktop computing services in environments where providing every user with a dedicated desktop PC is either too expensive or unnecessary.

Virtual desktop Infrastructure

Virtual desktop Infrastructure (VDI) relocates users' desktop environments from desktop PCs/laptops to remote servers and/or blade PCs, using a connection brokering service to assign users to individual desktop sessions. For users, this means they can access their desktop from any location, without being tied to a single client device. Since the resources are centralized, users moving between work locations can still access the same desktop environment with their applications and data.^[3] For IT administrators, this means a more centralized, efficient client environment that is easier to maintain and able to more quickly respond to the changing needs of the user and business.^[4]^[5]

Advantages and disadvantages

The shared resources model inherent in server hosted virtual desktops can offer advantages over the distributed desktops where every computer operates as a self-contained unit with its own processor, memory, and storage. Overall hardware expenses may diminish as users can share resources allocated to them on an as-needed basis. Virtualization potentially improves security of user data because all data can be located in the data center rather than on the local desktop.

Potential advantages include:

simpler provisioning of new desktops
lower cost of deploying new applications
desktop image-management capabilities
increased data security^[6]
longer refresh cycle for client desktop infrastructure
secure remote access to an enterprise desktop environment

Limitations of desktop virtualization include:

reliance of shared infrastructure can lead to performance degradation in incorrectly sized environments
challenges in setting up and maintaining drivers for printers and other peripherals
difficulty in running certain resource intensive applications
increased impact of downtime in the event of infrastructure failure
reliance on connectivity to corporate or public network prevents disconnected operation
complexity and high costs of VDI deployment and management^[7]

Local desktop virtualization

Local desktop virtualization implementations run the desktop environment on the client device, either directly on the physical hardware or on top of a hypervisor. Depending on the implementation both Type I and Type II hypervisors may be used. ^[8]

Local desktop virtualization is well suited for environments where continuous network connectivity cannot be assumed and where application resource requirements can be better met by using local system resources. However, local desktop virtualization implementations do not allow applications developed for system architecture to run on another. For example, while it is possible to used local desktop virtualization to run Windows 7 on a Apple Mac, as both use the same x86 architecture, it is not possible to run Windows 7 on an ARM-based tablet.^{[citation needed]}

References

^ Rouse, Margaret. "Desktop virtualization". TechTarget. Retrieved 1/3/2013. {{cite web}}: Check date values in: |accessdate= (help); More than one of |author= and |last= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
^ Keith Schultz (16). "Review: VDI without the server connection". InfoWorld. Retrieved 3 January 2013. One subset of VDI, dubbed client-hosted or offline mode {{cite web}}: Check date values in: |date= and |year= / |date= mismatch (help); Unknown parameter |month= ignored (help)
^ Chernicoff, David, “HP VDI Moves to Center Stage,” ZDNet, August 19, 2011.
^ Baburajan, Rajani, "The Rising Cloud Storage Market Opportunity Strengthens Vendors," infoTECH, August 24, 2011. It.tmcnet.com. 2011-08-24.
^ Oestreich, Ken, "Converged Infrastructure," CTO Forum, November 15, 2010. Thectoforum.com.
^ "Value of Virtual Desktops". Dell.com. Retrieved 2012-03-22.
^ Microsoft Windows Enterprise: Virtual Desktop Infrastructure VDI -- Virtual desktop infrastructure delivers the flexibility you need
^ "Desktop virtualization cheat sheet". Networkworld.com. Retrieved 2010-03-17.