How many virtual desktops can you support on a server using virtual desktop infrastructure (VDI) technology? Not enough for people to do it. But the new XenDesktop from Citrix Systems could change this.
The idea of running desktop applications back on host machines controlled and supported by the IT department is not new. Citrix and Microsoft have made a fortune on it over the past decade.
Citrix is hoping, like rival VMware and a bunch of other players, that a virtualization rev on this thin client computing model will finally get companies to adopt this VDI approach, which does not have the same limitations as host-thin client computing. But so far, the economics of VDI on the server side have been an issue even as potential savings and ease of management have been compelling for IT shops.
Earlier virtual desktop solutions, such as that provided by ClearCube, put a single Windows desktop instance on a blade server and fed this down the wire to a thin client. Over time, with virtualization hypervisors added into the mix, the number of desktops per server or per blade could be boosted.
VDI added another twist, allowing Windows instances to be displayed at desks or on laps using thin clients, desktop PCs or laptops. The hypervisor also allowed more Windows images to be supported by a single piece of iron.
With XenDesktop 3, announced today, Citrix has tweaked the Xen hypervisor underneath the server side of its VDI software stack so it can support roughly twice as many VDI seats. According to Calvin Hsu, director of product marketing at Citrix, the current crop of VDI offerings can maybe support between 20 and 25 virtual PC instances. That number is about the same regardless of the hypervisor used.
Citrix has some knowledge of how VMware's ESX Server hypervisor stacks up against its own XenServer hypervisor because XenDesktop is hypervisor agnostic and will support ESX Server or Microsoft's Hyper-V, should customers want. But with the XenDesktop 3 VDI package, Citrix has changed the underlying XenServer hypervisor so it can support an average of between 50 and 55 desktops per server. Those comparisons are for a current-generation X64 two-socket server using quad-core processors, which means you can get at best about seven virtual PCs per processor core.
The doubling up of virtual Windows seats required changes in the XenServer hypervisor because, as Hsu put it: "In the server world, you are not necessarily trying to cram as many VMs as you can get onto the server."
But when you are trying to sell VDI to CIOs in a tough economy and when end users are clutching their PCs, it is going to take a pretty compelling economic story to get people to give it a try. Cutting the server bill for VDI in half with some software tweaks is a good start.
XenDesktop 3 also includes a new feature called desktop streaming, which allows a single master image of a common corporate desktop to be streamed out to clients and run there (as opposed to being run in host mode back on the servers atop the hypervisor). This streaming approach is suitable for uses where desktop applications are virtually the same for all end users, such as in call centers.
A single desktop streaming server can store and distribute images for up to 500 end users, according to Hsu, and it has features that can start and idle pools of virtual machines to avoid a "boot storm" in the morning when people come in to work. The streaming server does not send a whole image of Windows down the wire, by the way, just the bits you need to boot and then the pieces that are required as you do your work.
However, you do need a license to Windows for all of those virtual seats - this is not a clever way to pirate software. Companies can also create private Windows images for individual or groups of users to suit their needs and then stream these through XenDesktop as well.
The updated VDI package from Citrix also has a new feature called Profile Manager. This works for hosted as well as for streamed desktops and captures all of the profile data that makes your Windows setup unique - personal settings for screens and apps, Web cache, and so forth - and stores them back in the data center so they can be applied to hypervisor hosted or desktop streamed Windows images served up by XenDesktop.
XenDesktop 3 includes a bunch of "high definition experience" or HDX technologies, as Citrix is branding them, to make the virtual desktop experience more like the local experience that a Windows user gets. Multimedia performance and peripheral support has been lacking in VDI setups and XenDesktop 3 has some software to fix these issues.
HDX MediaStream does not try to render multimedia back on the server but sends compressed data streams down to the endpoint PC or thin client and plays that media there. The HDX Plug-and-Play feature allows MP3 players, digital cameras, smart phones, scanners and other peripherals to plug into the virtual PC and be usable by the virtual Windows instance. Smart card authentication is also supported with the virtual PCs, which is necessary for government and financial sales.
As 2009 unfolds, Citrix will be adding other HDX technologies for XenDesktop as well as for its XenApp server (formerly known as Presentation Server) to allow real-time voice and video streaming, smart 3D rendering in applications that looks for the best device in the network (server or PC or thin client) to render 3D images and do so transparently to the end user, as well as network bandwidth and data caching extensions to boost the performance of applications running through XenDesktop or supported by XenApp servers.
XenDesktop 3 will be available this month. The Standard Edition costs $75 per virtual desktop if you use the XenServer hypervisor. If you want to use Hyper-V or ESX Server, you have to buy the software yourself and still pay $75 per seat. The Platinum Edition costs $395 per seat and includes thin client streaming, application management, performance monitoring and other features apparently wanted by big companies.
XenDesktop is, of course, distinct from the Project Independence type 1 hypervisor that Citrix and Intel are creating together for x64-based PCs. That hypervisor is a variant of XenServer that runs locally on the PC and will allow end users to have secure and distinct personal and business VMs set up on a single machine.
Citrix wants to be able to stream data down into that business VM and make some dough there, too. ®