It doesn't seem so long ago that analysts were predicting leaner, greener terminals that almost harked back to the original tenets of centralised computing... So where has the 'thin-client' concept ended up?
The virtual desktop PC can be delivered in many forms. You may see virtual images of an entire desktop complete with operating system, applications, and user profile delivered to various devices via virtual desktop infrastructure (VDI) initiatives. Or you may see thin clients, essentially stripped-down versions of the traditional desktop PC, which can host either complete virtual desktop images or only specific applications and trimmed down profiles. You'll even see the old terminal services model whereby the end device simply provides a window into applications and services that run entirely elsewhere on a data-centre server or mainframe computer, or other remotely located central-processing platform.
The distinction between all three approaches is becoming less well-defined, particularly in recent years as hybrid desktop virtualisation platforms, which split the workload between cloud-hosted virtual servers and local devices, have emerged.
The thin-client concept has been around for at least a decade in its current manifestation, and the advent of server virtualisation should in theory go hand-in-hand with the enterprise computing model. Market analyst Gartner forecast that 60 per cent of companies worldwide will have some form of VDI deployed by the end of 2012, up from 10 per cent in 2008, with vendors pushing VDI, thin client and terminal services capabilities hard, including Citrix, Dell (which purchased thin-client specialist Wyse in April 2012), EMC, Hewlett-Packard (HP), and Microsoft.
While organisations buy fewer standard PCs and laptops for their desktops, the rise of enterprise mobility has meant that the thin-client market has not taken over the desktop computing requirement as some predicted. Where, then, does that leave the thin end of the market?
As with all technology, cost and return-on-investment, arguments for thin-client and virtual-desktop deployment are often misleading and depend on many variables. These include whether IT departments choose to procure thin-client hardware or push virtual desktops on to legacy desktop devices, and what other upgrades need to be made in the back-end servers and'local' 'and wide-area networks.
Putting capital expenditure to one side, ongoing savings appear genuinely significant from reduced hardware and software maintenance and management overheads. With desktops virtualised alongside servers in the data centre, back-ups become easier to run with operating system and application upgrades, and patch management simpler to perform.
Scaled-down hardware options on thin clients and other end-point hosting devices also mean fewer fixes or upgrades to physical components. Citrix product manager Patrick Irwin says: "You don't need to go and get something new out of the cupboard, or have people rushing around trying to fix things."
While the drivers for the adoption of desktop virtualisation technology are the same as ever, IT departments - and end-users familiar with virtualisation and cloud-hosted service models that deliver on-demand compute resources, workloads and applications in the form of infrastructure as a service (IaaS) and software as a service (SaaS) - now seem more confident in adopting the desktop as a service (DaaS) model as well.
"The key thing driving the adoption of thin clients now is the pick-up in desktop virtualisation, a move to centralisation, and delivering IT-as-a-service as a way of bringing the desktop PC into the data centre," says Irwin. Improvements to thin-client virtualisation and remote display protocol technology have also enabled a new generation of virtual applications to run efficiently on devices other than desktop PCs for the first time.
"Virtual desktops give devices independent access mechanisms for traditional legacy desktop PC software and other types of applications," adds Brian Gammage, chief marketing technologist for end-user computing at EMC-owned virtualisation leader VMware.
Graphics and peripheral attachment capabilities
Thin-client processing, storage and power consumption metrics have invariably improved, alongside graphical processing units (GPUs) able to deal with 3D rendering more efficiently. Dell Wyse's most powerful thin-client devices are now based on dual core processors and come with high-performance graphics capabilities in small form-factors that lose only 15W of power, for example.
HP is another big hardware vendor with a heritage in delivering thin clients which has continued to make substantial investments in the technology. The company introduced new systems earlier this year - including the T410 - costing $429 (£266) for a device based on an ARM 1.8GHz CPU that sports an 18.5in display, power over Ethernet connectivity (which removes the need for a power socket), and electricity consumption of 13W.
Solutions have emerged that improve the throughput of graphics processing from the central server using better compression technology and WAN optimisation to render complex 3D images on remote screens more quickly, and provide better access to the multimedia capabilities on the local device itself - both of which thin-client devices and desktop virtualisation platforms have previously struggled to do.
"The market has changed within the last three to five years - partly just maturity but also fixing some of the things in the technology, being able to deliver things which thin clients previously could not do," says David Angwin, marketing director at Dell Wyse. "[For instance,] how do you handle peripherals or using multiple 2600x1600 resolution screens common in the oil and gas industries and finance sectors?"
Fitting for purpose: the new usage scenarios
Those technology improvements have also made it easier to fit individual applications and workloads with differing requirements to more specific types of delivery, splitting application streaming more suited to terminal services environments from full VDI, for example. Vendors have become much more adept at identifying usage scenarios where they can split the workload between the back end and the user device. Some - but not all - ruefully admit that they may have stymied virtual desktop adoption in the past because they centred on a one-size-fits-all approach, which did not take into account the requirements of specific user groups and applications for which VDI made most practical and financial sense.
"The better approach is to look at different user groups, what applications and content they need, whether it is just data or voice and data too, as well as peripheral requirements, then decide what virtual technology and device is appropriate," says Angwin.
"I do not agree that VDI did not take off," insists VMware's Brian Gammage. "It is already grounded for success. In the world of the desktop fits all, where there is now a much more diverse set of assets and capabilities, we always felt it was wrong for us to replace the PC with a new type of PC, whether the desktop is virtualised or not. The general trajectory for thin-client adoption is pretty much on track - EMC does not break out numbers, but a good part of VMware's business is VDI and it seems to be keeping others in clover as well."
Angwin explains: "The Web is starting to increase as a way of consuming applications, particularly for groups of users that only need to access this one back-end system, meaning you can just give them a device with a Web browser." That workload is such that you never get enough users on the server to warrant VDI, so the tendency is to put desktop workstations in the data centre and use one of the new high-performance protocols - VMware View PCoIP, Citrix HDX 3D Pro, Microsoft RemoteFX - to deliver other applications to a local device.
One high-performance protocol is the high-definition experience (HDX) 3D Pro from Citrix, first released in 2009 to support host-side applications on the vendor's XenDesktop virtual desktop platform and focused on optimising graphics-intensive workloads within virtual desktops by using compression codecs and WAN (wide-area network) optimisation. As such it enables all sorts of applications such as CAD/CAM, engineering, and architectural design software for use in a variety of different industries on the thin client for the first time.
Teradici's PC-over-IP (PCoIP) protocol, built into VMware's View desktop virtualisation software, does a similar job but in a slightly different way. It contains a map of the pixels of the desktop client display and only transmits changed pixels rather than the whole image to that device, for example,'with output optimised according to specific device and network bandwidth available (i.e. output definition is downscaled to match the definition on the local screen if it is lower).
Elsewhere, Microsoft's RemoteFX is aimed at thin-client users who need to use 3D directX acceleration over a remote session, as well as USB redirection that allows peripheral devices to be plugged in and accessed.
Elsewhere HP has won plaudits for adopting an agnostic approach to the underlying desktop virtualisation strategy, using its own Zero Core operating system to give end-users a choice of multiple virtual desktop environments via support of the Citrix ICA HSX MediaStream, Microsoft RDP/RFX, Teradici PCoIP, as well as VMware View 5.0 protocols.
Vendors also spot an opportunity for virtual desktops to support audio and video applications in call centres and other environments where staff require unified communication suites to support voice over IP (VoIP), video conferencing, and instant messaging applications but very little else. "With multimedia, video decoding is a heavy workload and it is better to send that down to the device and have the device decode it rather than do it in the data centre," says Angwin. "But we also see unified communications coming on-board where we need to do a mix."
EMC also proposes virtual desktops as suitable for unified communications applications, based on Cisco virtualisation infrastructure experience (VXI) technology that combines back-end network, load balancing, application delivery, and WAN optimisation components with Citrix XenDesktop and EMC VMware View desktop virtualisation software. A range of end-point devices have been certified for use with the system, including Cisco IP telephone handsets, tablets and smartphones, as well as thin clients from Dell Wyse, DevonIT, and Igel, here highlighting the broad extent of the close partner relationships between the major vendors looking to control the desktop virtualisation market.
Repercussions for enterprise ICT managers?
Inevitably, there is a flip side to the broader use of thin clients and virtual desktops to support a wider range of applications and user requirements, with TCO and management benefits coming at a price.
The successful implementation of any VDI initiative means a lot of groundwork for the hard-pressed in-house ICT staff, which will include making sure the available LAN (local area network) and WAN infrastructure is up to scratch and, if not, building the necessary safeguards into the design of whichever virtual desktop or application platform is deployed. "You are completely at the mercy of network capabilities if you are dealing with a thin-client device," says Gammage at VMware.
"You have got to have adequate bandwidth down to remote sites. Some organisations will accept that and make sure it is built into the project requirements, but others have so many sites it is either not practical or physically impossible to reach, with oil and gas companies for example," says Angwin. "There will always be times where remote connectivity will go down, and that is where centrally managed streamed solutions stored in the data centre but synced with a local server come in."
ICT managers then have to settle on the client device to host the virtual desktop, a decision often influenced more by financial necessity than preference for one type of platform above another.
"It depends on the project - some companies are repurposing existing desktop PCs, in effect turning them into thin clients with lower maintenance costs and longer lifecycles," says Citrix's Patrick Irwin, "but if it is a new build, with all the carbon reduction and environmental initiatives, it is a chance to wipe the slate clean [with new hardware]."
The complexity involved in configuring VDI to run on multiple thin-client devices, and running VDI instances from different software companies on standardised hardware, also gives IT managers cause for concern, especially when retrofitting legacy environments.
Some advances have been made with virtual desktop management software, while HP has developed an auto-sensing technology which it says identifies the VDI platform its T410 is connecting to and reprogramming itself to the Citrix, Microsoft, or VMware software as soon as it is connected to the host server via the network.
Implementing virtual desktops can also introduce headaches around operating system and application licensing, especially where big software companies fail to make provision for, or properly explain, enterprise licensing agreements. Almost none of the big enterprise software vendors have definitively solved how to adapt their licences to run on physical and virtual environments spanning multiple devices and access methods, for example, leading to confusion and a requirement to introduce more software licence-management applications into an already complex, pricey mix.
"Those issues have not gone away, there are still a lot of niggles there," says Irwin at Citrix. "Lots of people still want to get away from paying for licences for Windows delivered in virtual machines, and Microsoft still needs licence approbation for users."
Nonetheless, the thin-client concept is proving to be an enduring one for some sectors; and that's before the potential for other 'thin' endpoint devices, such as thin POS, come under consideration.