Difference between revisions 134631183 and 134653638 on dewiki

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'''Desktop virtualization''' is software technology that separates the [[desktop environment]] and associated [[application software]] from the physical client device that is used to access it.

'''Desktop virtualization''' is the concept of isolating a logical operating system instance from the client that is used to access it.

'''Desktop-Virtualisierung''' ist ein Sammelbegriff, der Softwaretechnologien beschreibt, die die Portierbarkeit, Verwaltbarkeit und Kompatibilität mit Anzeigegeräten für die Desktopumgebung eines PC's erhöhen, indem die Ausführung von Anwendungen vom physischen Anzeigegeräte getrennt wird. Eine verbreitete Implementierung dieser Technologie ist es, mehrere Desktopsysteme auf einer leistungsfähigen Serverhardware mit Hilfe eines Hypervisors auszuführen und zum Zugriff und zur Anzeige der Bildschirminhalte verschiedene Anzeigeeräte (zum Beispiel sog. Thin-Clients, Desktop-PC's oder mobile Geräte) zu verwenden. Die Infrastruktur zur Bereitstellung solcher Umgebungen wird in der Regel als Virtual Desktop Infrastructure, kurz VDI, bezeichnet.⏎
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Desktop virtualization can be used in conjunction with [[application virtualization]] and ([[Windows]]) user profile management systems, now termed "user virtualization," 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 and backed up through traditional redundant maintenance systems.  If a user's device or hardware is lost, the restore is much more straightforward and simple, because basically all the components will be present at login from another device.  In addition, because no data is 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.  Below are more detailed descriptions of the types of desktop virtualization technologies that will be used in a typical deployment.

== System architectures ==
Desktop virtualization implementations are classified based on ifwhere 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 and whether or not, the virtual desktop persists between sessions.<ref>{{cite web
   |last1=Rouse
   |first1=Margaret
   |last2=Madden
   |first2=Jack
   |title=Desktop virtualization
   |url=http://searchvirtual  desktop persists between sessions. Typically, s.techtarget.com/definition/desktop-virtualization|publisher=TechTarget|accessdate=1/3/2013}}</ref> Software products that deliver desktop virtualization solutions can combine local and remotethese two implementation methods into a single product to provide the most appropriate implementation to support specific to requirements.  The degree 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]]. (Summarizing from.<ref>{{cite web
   |last1=Rouse
   |first1=Margaret
   |last2=Madden
   |first2=Jack
   |title=Desktop virtualization
   |url=http://searchvirtualdesktop.techtarget.com/definition/desktop-virtualization|publisher=TechTarget|accessdate=1/3/2013}}</ref>)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 a [[client/server]] computing environments. Application execution takes place on a remote operating system which is linked to 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]] device, a [[tablet computer|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.<ref>{{cite web|title=Review(contracted; show full)

However, VDI implementations allow for delivering a personalized workspace back to a user, which retains all the user's customizations.  There are several methods to accomplish this.  One is to deliver fully persistent VM desktops, in which a user gets a dedicated desktop that functions essentially as their own PC.  Another mode is to deliver non-persistent desktops which do not include user personalization.  These are VM desktops delivered from a pool which 
are then used for a session and returned to the pool.  This approach has the advantage of keeping VM desktops "clean" as nothing is saved to the image by the user.  Non-persistent desktops can be paired with user virtualization technologies to deliver user profiles and customizations(and all profiles settings, application data settings, configuration and user data), to the user upon login.  The user profile is matched with a non-persistent desktop providing an experience that is very little different from a PC.  All changes made to the user profile are saved to the profile and are restored to the user upon their next login.  However, the VM is returned to the pool with no changes saved to it.

=== 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. Examples of enterprise application virtualization software include [[Citrix XenApp]], [[Microsoft App-V]], [[VMware ThinApp]] and [[Systancia|Systancia AppliDis]].  Liquidware Labs offers a slightly different approach to application virtualization with its FlexApp feature in its ProfileUnity solution.  FlexApp does not virtualize the application, instead it virtualizes the location of the application.

=== 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 ====
{{For|Data as a Service (DaaS)|Data as a service}}

Remote desktop virtualization can also be provided via a [[Cloud computing]] similar to that provided using a [[Software as a service]] 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 compute, 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. For example, VMware's Horizon DaaS, based on VMware's acquisition of Desktone, is a monthly fixed rate DaaS service.<ref>http://www.vmware.com/products/daas</ref>  Amazon's WorkSpaces on Amazon EC2 is also a monthly fixed rate.<ref>http://aws.amazon.com/workspaces</ref> 

Cloud hosted virtual desktops can be implemented using both VDI and Remote Desktop Services-based systems and can be provided through public cloud, private cloud infrastructure, and hybrid cloud platforms. Private Cloud implementations are commonly referred to as "Managed VDI". Public Cloud offerings tend to be based on Desktop-as-a-Service technology.{{Citation needed|date=January 2013}}

The US Company Desktone has the trademarks on the expressions "desktops as a service" and "DaaS" from the U.S. Patent and Trademark Office <ref>http://thevarguy.com/virtualization-applications-and-technologies/desktone-trademarks-desktop-service-and-daasthen used for a session and returned to the pool.  This approach has the advantage of keeping VM desktops "clean" as nothing is saved to the image by the user.  Non-persistent desktops can be paired with user virtualization technologies to deliver user profiles and customizations(and all profiles settings, application data settings, configuration and user data), to the user upon login.  The user profile is matched with a non-persistent desktop providing an experience that is very little different from a PC.  All changes made to the user profile are saved to the profile and are restored to the user upon their next login.  However, the VM is returned to the pool with no changes saved to it.

=== 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. Examples of enterprise application virtualization software include [[Citrix XenApp]], [[Microsoft App-V]] and [[VMware ThinApp]].  Liquidware Labs offers a slightly different approach to application virtualization with its FlexApp feature in its ProfileUnity solution.  FlexApp does not virtualize the application, instead it virtualizes the location of the application.

=== 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 ====
{{For|Data as a Service (DaaS)|Data as a service}}

Remote desktop virtualization can also be provided via a [[Cloud computing]] similar to that provided using a [[Software as a service]] model. This approach is usually referred to as Desktop-as-a-Service (DaaS). The DaaS provider typically takes full responsibility for hosting and maintaining the compute, 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. {{Citation needed|date=January 2013}}

DaaS can be implemented using both VDI and Remote Desktop Services-based systems. DaaS can be provided through public cloud, private cloud infrastructure, and hybrid cloud platforms.{{Citation needed|date=January 2013}}

The US Company Desktone has the trademarks on the expressions "desktops as a service" and "DaaS" from the U.S. Patent and Trademark Office <ref>http://thevarguy.com/virtualization-applications-and-technologies/desktone-trademarks-desktop-service-and-daas</ref>

While it is very likely that Desktone will be unable to enforce the trademarks, Desktone's intention was to clearly define that desktops as a service (DaaS) specifically describes an outsourced subscription service for server-hosted desktops - ideally powered by a Desktone Platform and delivered by Desktone-certified service providers. Desktone has stated that  DaaS is not any of the client computing models that have appropriated the term to mean enterprise VDI where the organization owns the infrastructure used to deliver hosted virtual desktops to its end users; or streaming virtual desktops to client machines where the VMs are cached and executed locally; or server-based computing built on shared service environments like Terminal Services; or webtops that don't provide a true Windows client experience.For Desktone the meaning of DaaS resides in outsourcing the VDI to a service provider. Indeed, Desktone believes enterprises won't achieve their operational and economic goals otherwise, it says. Simply enabling PCs as an internally provisioned network service isn't enough.<ref>http://virtualization.sys-con.com/node/978606</ref>

=== Local desktop virtualization ===
Local desktop virtualization implementations run the [[desktop environment]] on the client device using [[hardware virtualization]] or [[emulator|emulation]]. For hardware virtualization, depending on the implementation both Type I and Type II [[hypervisor]]s may be used.<ref>{{cite web|url=http://www.networkworld.com/news/2009/112409-vdi-desktop-virtualization-cheat-sheet.html |title=Desktop virtualization cheat sheet |publisher=Networkworld.com |dat(contracted; show full)* [[Remote desktop software]]
* [[Comparison of remote desktop software]]
* [[Web desktop]]

== References ==
<references/>

== 
WeblinksFurther reading ==
* Paul Venezia (April 13, 2011) [http://www.infoworld.com/d/virtualization/virtualization-shoot-out-citrix-microsoft-red-hat-and-vmware-666 Virtualization shoot-out: Citrix, Microsoft, Red Hat, and VMware. The leading server virtualization contenders tackle InfoWorld's ultimate virtualization challenge], ''[[InfoWorld]]''
* Keith Schultz (December 14, 2011) [http://www.infoworld.com/d/virtualization/vdi-shoot-out-citrix-xendesktop-vs-vmware-view-181691 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) [http://www.infoworld.com/t/virtualization/vdi-shoot-out-hdx-vs-pcoip-181662 VDI shoot-out: HDX vs. PCoIP. The differences between the Citrix and VMware remote desktop protocols are more than skin deep], ''InfoWorld''
* [http://www.bitkom.org/files/documents/LF_Desktop-Virtualisierung.pdf Leitfaden Desktop-Virtualisierung des Bundesverbands Informationswirtschaft,Telekommunikation und neue Medien e. V. (BITKOM), BITKOM, 2012]
* [http://www.itwissen.info/definition/lexikon/VDI-virtual-desktop-infrastructure.html IT-Wissen:VDI (virtual desktop infrastructure)]
* [http://www.computerwoche.de/a/was-ist-was-bei-microsoft-virtual-desktop-infrastructure,2556457 Microsoft-VDI-Ratgeber:Was ist was bei Microsoft Virtual Desktop Infrastructure?]

== External links ==
* xrdp open source Remote Desktop Protocol server [http://www.xrdp.org/ xrdp]
* [http://www.vesk.com VESK Largest privately owned Virtual Desktop in the UK]

{{DEFAULTSORT:Desktop Virtualization}}⏎
== External links ==
* xrdp open source Remote Desktop Protocol server [http://www.xrdp.org/ xrdp]

{{DEFAULTSORT:Desktop Virtualization}}
[[Category:Centralized computing]]
[[Category:Remote desktop]]
[[Category:Thin clients]]

[[fr:Virtual Desktop Infrastructure]]