Desktop virtualization is a software technology that separates the
desktop environment
In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a graphica ...
and associated
application software
Application may refer to:
Mathematics and computing
* Application software, computer software designed to help the user to perform specific tasks
** Application layer, an abstraction layer that specifies protocols and interface methods used in a c ...
from the physical client device that is used to access it.
Desktop virtualization can be used in conjunction with
application virtualization
Application virtualization is a software technology that encapsulates computer programs from the underlying operating system on which they are executed. A fully virtualized application is not installed in the traditional sense, although it is stil ...
and user profile management systems, now termed
user virtualization
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User virtualization refers to the independent management of all aspects of the user on the desktop environment. User virtualization decouples a user's profile, settings and data from the operating system and stores this in ...
, to provide a comprehensive desktop environment management system. In this mode, all the components of the desktop are virtualized, which allows for a highly flexible and much more secure desktop delivery model. In addition, this approach supports a more complete desktop disaster recovery strategy as all components are essentially saved in the
data center
A data center (American English) or data centre (British English)See spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunic ...
and backed up through traditional redundant maintenance systems. If a user's device or hardware is lost, the restore is straightforward and simple, because the components will be present at login from another device. In addition, because no data are saved to the user's device, if that device is lost, there is much less chance that any critical data can be retrieved and compromised.
System architectures
Desktop virtualization implementations are classified based on whether the virtual desktop runs remotely or locally, on whether the access is required to be constant or is designed to be intermittent, and on whether or not the virtual desktop persists between sessions. Typically, software products that deliver desktop virtualization solutions can combine local and remote implementations into a single product to provide the most appropriate support specific to requirements. The degrees of independent functionality of the client device is necessarily interdependent with the server location and access strategy. And virtualization is not strictly required for remote control to exist. Virtualization is employed to present independent instances to multiple users and requires a strategic segmentation of the host server and presentation at some layer of the host's architecture. The enabling layer—usually application software—is called a
hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is calle ...
.
Remote desktop virtualization
Remote desktop virtualization implementations operate in a
client/server computing environment. Application execution takes place on a remote operating system which communicates with the local client device over a network using a remote display protocol through which the user interacts with applications. 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
In computer networking, a thin client is a simple (low-performance) computer that has been optimized for establishing a remote connection with a server-based computing environment. They are sometimes known as ''network computers'', or in th ...
device, a
tablet
Tablet may refer to:
Medicine
* Tablet (pharmacy), a mixture of pharmacological substances pressed into a small cake or bar, colloquially called a "pill"
Computing
* Tablet computer, a mobile computer that is primarily operated by touching the s ...
, or even a
smartphone
A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
. A common implementation of this approach involves hosting multiple desktop operating system instances on a server hardware platform running a
hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is calle ...
. Its latest iteration is generally referred to as Virtual Desktop Infrastructure, or "VDI" (note that "VDI" is often used incorrectly to refer to any desktop virtualization implementation).
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, smartphones, and non-Windows-based desktop PCs and laptops).
Remote desktop virtualization can also provide a means of resource sharing, to distribute low-cost desktop computing services in environments where providing every user with a dedicated desktop PC is either too expensive or otherwise unnecessary.
For IT administrators, this means a more centralized, efficient client environment that is easier to maintain and able to respond more quickly to the changing needs of the user and business.
Presentation virtualization
Remote desktop software allows a user to access applications and data on a
remote computer
In computing, the term remote desktop refers to a software- or operating system feature that allows a personal computer's desktop environment to be run remotely off of one system (usually a PC, but the concept applies equally to a server (comp ...
over a network using a remote-display protocol. A VDI service provides individual desktop operating system instances (e.g., Windows XP, 7, 8.1, 10, etc.) for each user, whereas remote desktop sessions run in a single shared-server operating system. Both session collections and virtual machines support full desktop based sessions and remote application deployment.
The use of a single shared-server operating system instead of individual desktop operating system instances consumes significantly fewer resources than the same number of VDI sessions. At the same time, VDI licensing is both more expensive and less flexible than equivalent remote desktop licenses. Together, these factors can combine to make remote desktop-based remote desktop virtualization more attractive than VDI.
VDI implementations allow for delivering personalized workspace back to a user, which retains all the user's customizations. There are several methods to accomplish this.
Application virtualization
Application virtualization improves delivery and compatibility of applications by encapsulating them from the underlying operating system on which they are executed. A fully virtualized application is not installed on hardware in the traditional sense. Instead, a hypervisor layer intercepts the application, which at runtime acts as if it is interfacing with the original operating system and all the resources managed by it when in reality it is not.
User virtualization
User virtualization separates all of the software aspects that define a user’s personality on a device from the operating system and applications to be managed independently and applied to a desktop as needed without the need for scripting, group policies, or use of roaming profiles. The term "user virtualization" sounds misleading; this technology is not limited to virtual desktops. User virtualization can be used regardless of platform – physical, virtual, cloud, etc. The major desktop virtualization platform vendors, Citrix, Microsoft and VMware, all offer a form of basic user virtualization in their platforms.
Layering
Desktop layering is a method of desktop virtualization that divides a disk image into logical parts to be managed individually. For example, if all members of a user group use the same OS, then the core OS only needs to be backed up once for the entire environment who share this layer. Layering can be applied to local physical disk images, client-based virtual machines, or host-based desktops. Windows operating systems are not designed for layering, therefore each vendor must engineer their own proprietary solution.
Desktop as a service
Remote desktop virtualization can also be provided via
cloud computing
Cloud computing is the on-demand availability of computer system resources, especially data storage ( cloud storage) and computing power, without direct active management by the user. Large clouds often have functions distributed over mul ...
similar to that provided using a
software as a service
Software as a service (SaaS ) is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted. SaaS is also known as "on-demand software" and Web-based/Web-hosted software.
SaaS is con ...
model. This approach is usually referred to as cloud-hosted virtual desktops. Cloud-hosted virtual desktops are divided into two technologies:
# Managed VDI, which is based on VDI technology provided as an outsourced managed service, and
# Desktop as a service (DaaS), which provides a higher level of automation and real multi-tenancy, reducing the cost of the technology. The DaaS provider typically takes full responsibility for hosting and maintaining the computer, storage, and access infrastructure, as well as applications and application software licenses needed to provide the desktop service in return for a fixed monthly fee.
Cloud-hosted virtual desktops can be implemented using both VDI and Remote Desktop Services-based systems and can be provided through the public cloud, private cloud infrastructure, and hybrid cloud platforms. Private cloud implementations are commonly referred to as "managed VDI".
Public cloud
Cloud computing is the on-demand availability of computer system resources, especially data storage (cloud storage) and computing power, without direct active management by the user. Large clouds often have functions distributed over multi ...
offerings tend to be based on desktop-as-a-service technology.
Local desktop virtualization
Local desktop virtualization implementations run the
desktop environment
In computing, a desktop environment (DE) is an implementation of the desktop metaphor made of a bundle of programs running on top of a computer operating system that share a common graphical user interface (GUI), sometimes described as a graphica ...
on the client device using
hardware virtualization
Hardware virtualization is the virtualization of computers as complete hardware platforms, certain logical abstractions of their componentry, or only the functionality required to run various operating systems. Virtualization hides the physica ...
or
emulation
Emulation may refer to:
*Emulation (computing), imitation of behavior of a computer or other electronic system with the help of another type of system
:*Video game console emulator, software which emulates video game consoles
*Gaussian process em ...
. For hardware virtualization, depending on the implementation both Type I and Type II
hypervisor
A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is calle ...
s may be used.
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 always allow applications developed for one system architecture to run on another. For example, it is possible to use local desktop virtualization to run Windows 7 on top of
OS X
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...
on an
Intel-based Apple Mac, using a hypervisor, as both use the same
x86
x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was introd ...
architecture.
See also
*
Virtual machine
In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardw ...
References
Further reading
* Paul Venezia (April 13, 2011
Virtualization shoot-out: Citrix, Microsoft, Red Hat, and VMware. The leading server virtualization contenders tackle InfoWorld's ultimate virtualization challenge ''
InfoWorld
''InfoWorld'' (abbreviated IW) is an information technology media business. Founded in 1978, it began as a monthly magazine. In 2007, it transitioned to a web-only publication. Its parent company today is International Data Group, and its siste ...
''
* Keith Schultz (December 14, 2011
VDI shoot-out: Citrix XenDesktop vs. VMware View. Citrix XenDesktop 5.5 and VMware View 5 vie for the most flexible, scalable, and complete virtual desktop infrastructure ''InfoWorld''
* Keith Schultz (December 14, 2011
VDI shoot-out: HDX vs. PCoIP. The differences between the Citrix and VMware remote desktop protocols are more than skin deep ''InfoWorld''
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Centralized computing
Remote desktop
Thin clients
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