I was getting a bit confused by all the different terms used by vendors like Citrix for ways to present datacenter executed desktops to end-users. This post is an attempt to make clear what vendors and analyst firms like Gartner mean.
Basically there are two techniques to execute desktops in a datacenter and present it to end-users:
Server Based Computing (SBC). Also known as ‘presentation virtualization’ and ‘session virtualization’. Invented by Citrix when it launched WinFrame in 1995. It basically is able to host multiple user sessions on a single operating system. Each user session is able to run it’s own user environment and applications. WinFrame evolved to the current Citrix XenApp. Microsoft acquired the code of Citrix and started it’s own product named Terminal Services. Currently this is called Remote Desktop Services. Both Citrix and Microsoft solutions allow to present individual applications or full desktops.
Virtual Desktop Infrastructure (VDI). VMware is inventor of the VDI-technology. It introduced Virtual Desktop Manager 2.0 at January 24 2008. This was the first VDI solution on the market which involved to the current VMware Horizon View. Citrix released competitor XenDesktop in 2009.
Using VDI each user session runs on a seperate operating system running as a vitual machine hosted by a hypervisor.
VDI is in most scenarios used to present a full desktop to the enduser. Citrix offers in XenDesktop a way to present a single application in a VDI session.(VM hosted apps)
For VDI many other terms used. One of the reasons is that VMware has legal rights on the name VDI. To prevent copyright issues some vendors decide to use a slightly different naming. Another reason is because different implementations are used in VDI like server and client operating systems.
- Hosted Virtual Desktops (HVD). Same as VDI but Gartner uses this to prevent copyright issues
- Centralized Virtual desktops (CVDs)= Same as VDI. Used by IDC
- Server-hosted virtual desktops (SVHD)= Same as VDI. Mainly used by analyst firms.
- Hosted VDI Desktops (1-to-1 Windows 7/8)= VDI. Term used by Citrix.
- hosted private desktop = VDI. Term used by Citrix
- Server VDI = VDI . A term used by Citrix. It is VDI delivered by Citrix XenDesktop
- Personal VM-based VDI= VDI where each user has its own, persistent environment stored on unique virtual disks. Applications which are installed by the user remain available even when session has ended.
- Pooled VM-based VDI= VDI in which the user environment is reset after the session has ended.
- Server VDI Workers (VM/Server Isolation) = VDI. A term used by Citrix. In this configuration virtual machines are running Windows Server as a guest operating system without Remote Desktop Services enabled. Each instance is used by a single end user. In most cases a Windows 7/8 look and feel is applied. Citrix XenDesktop is used to run these Windows Server vm’s. The reason to use Windows Server as a operating system for end users is Microsoft not allowing to use Windows client operating systems in multi-tenant infrastructures with shared hardware.
Server based computing terms
- Session-Based VDI = SBC. Term used for Remote Desktop Services of Microsoft
- Session virtualization= SBC.
- Presentation Virtualization= SBC
- Terminal Services= The old name for what now is called Microsoft Remote Desktop Services.
- Hosted-Shared Desktop (multi-user RDS) = SBC. Term used by Citrix which is in fact just Citrix XenApp running on top of Remote Desktop Services
- MetaFrame, WinFrame, Presentation Server = SBC. Old names for what is now called Citrix XenApp
some other terms for presenting desktops used are:
cloud-hosted desktops = Also known as Desktop as a Service (DaaS). A set of applications or a full desktop are consumed by end users. The infrastruture to offer these is managed by a service provicer.
VM hosted apps/ VM hosted applications = Uses Citrix XenDesktop to present a single application to the end user instead of a full desktop. Acts as an alternative for published applications available in XenApp.