VDI (Virtual Desktop Infrastructure) is different from traditional virtualization of servers because, unlike servers which provide services exclusively onto a network, desktops are a point of physical interaction with end users. There is no escaping the need for there to be physical equipment that the end users will actually touch. Keyboards, mice, touchscreens, monitors, speakers… these things cannot be virtualized.
Because of this VDI faces much more complicated decision making and planning than virtualizing servers would. VDI physical requirements can have a wide variety of solutions.
Traditionally we approached VDI and terminal servers’ needs around physical interaction through the use of thin clients. Thin clients sit on the network and utilize the same protocols and techniques we would use for normal remote graphical access with protocols like NX, ICA, RDP and VNC. A thin client runs a full operating system but one that is very lean and that has a singular purpose – to manage connections to other machines. The idea of the thin client is to keep all processing remote and only have the necessary components on the local hardware to handle networking and local interactions. Thin clients are relatively low cost, low power consumption, easy to maintain, reliable and have very long lifespans. But they don’t cost so little as to not be a concern, typically prices are half to three quarters the cost of a traditional desktop and while they tend to last up to twice as long in the field, this remains neither a trivial cost for initial acquisition nor a trivial long term investment cost.
Because of the remaining high costs of traditional thin clients a more modern replacement, the zero client, has arisen as a fix to those issues. A zero client is not a strict term and is truly just a class of thin clients but one that has removed traditional processing involving a CPU and moved to dedicated very low cost remote graphical processing that is essentially nothing more than a display adapter attached to a network. Doing so reduces the power needs, management needs and manufacturing costs allowing for a much lower cost end point device. Zero Clients offer few potential features than do Thin Clients which can often run their own apps like a web browser locally, as there is no local processing but this is often a good thing rather than a bad thing. Supporting Zero Clients is also a new breed of remote graphical protocols often associated with them such as PCoIP.
Of course, going in the other direction, we can use full fat clients (e.g. traditional desktops and laptops) as our clients. This generally only makes sense if either the desktops are remnants of a previous infrastructure and only being repurposed as remote graphical access points or if the infrastructure is a hybrid and users use the desktops for some purposes and the VDI or terminal services for others. In some cases where thin clients are desired and fat clients are available at low cost, such as off lease with older units, fat clients can still make financial sense but the use cases there are limited. It is extremely common to use existing fat clients during a transition phase and then to migrate to thin or zero clients once a desktop refresh point has been reached or on a machine by machine basis as the machines require maintenance.
Today other options do exist such as using phones, tablets and other mobile devices as remote access points but these are generally special cases and not the norm due to a lack of good input devices. But use cases do exist and you can see this from time to time. As devices such as Android-based desktops begin to become more common on the market we may find this becoming more standard and may even see some rather unexpected situations where even devices like advanced desktop phones that run Android will be used as a phone and a thin client device at once. The more likely situation is that convertible cell phones that can double as lightweight desktop devices when docked will be popular thin client choices.
The last hardware consideration is that of BYOD or “Bring Your Own Device.” When moving to VDI and/or Terminal Services infrastructures the ability to leverage employee devices becomes very good. There are legal and logistical complications with employees supplying all of their own access devices but there are huge benefits as well such as happier employees, lower costs and more flexibility. The use of remote graphical displays rather than exposing data directly vastly reduces security risk and changes how we can approach accessing and exposing internal systems.
It is easy to become caught up in the move of processing resources from local to server when looking at VDI and to overlook that hardware costs remain, and generally remain quite significant, on a per user “on the desktop” level. Pricing out VDI is not as simple as determining the cost of a VDI server to replace the cost of desktops. A cost reduction per desktop must be determined and can easily be significant but can just as easily be pretty trivial. The cost of desktops or desktop replacement hardware will continue to be a large part of the per user IT budget even with VDI solutions.