You know an IT concept has real value when its meaning starts being obfuscated, when a lot of people want to take a ride on the hype train. This is where we’re at today with thin clients. There’s a lot of debate about how thin these devices must be to be truly worthy of the name, or how thick they can be while still delivering most of the advantages.
Thin clients are those that, one way or another, do without hardware or software that was previously considered essential. These skinny devices usually lack floppy and hard drives, and they employ as little memory and processing power as they can reasonably get away with.
When you are attempting to evaluate desktop devices for thinness, you should use the locations where processing and storage are actually carried out as criteria. The ultimate, original thin client was an ASCII terminal—a keyboard and screen unit that merely echoes characters sent from a remote location. That’s too thin for most of today’s needs, but many other options exist.
A true thin client should be stateless. In other words, applications and data are stored on a server (ideally, so should the client device’s OS, if one is even required). Clients acquire a state only when a user switches one on and logs on to a server. Management, therefore, is unnecessary, and users can roam from desk to desk seamlessly.
Sometimes termed a thin client (but actually rather toward the thick end of the scale) is the Network PC, or NetPC, offered by Compaq (the iPaq), Dell (the WebPC), Hewlett-Packard (the e-Vectra), and others. NetPCs use standard Intel processors and Windows OSs, but they have been “locked down” in that they have neither floppy drives nor expansion slots. Peripherals, if any, are connected via Universal Serial Bus (USB) ports.
Omitting local storage and booting NetPCs from a server, as with yesterday’s “diskless workstations,” is feasible, at least for those that contain the required boot ROMs. However, most implementations include local hard drives, sometimes trendily redubbed “cache” and sometimes not. Therefore, NetPCs are vulnerable to hard disk failure.
Because NetPCs are designed to execute applications locally, they need all the processing power and memory upgrades of an ordinary PC, with the early obsolescence that implies. If, in addition, administrators attempt to achieve statelessness by storing all applications on servers, then there is a significant effect on network bandwidth consumption.
Another thin-client wannabe is the NC developed by IBM, Oracle, and Sun Microsystems. Truly thin by virtue of its statelessness, this downloads its OS as it boots, then executes Java applications both locally and remotely. Problems? Apart from the lack of coveted Windows support, the demand for network bandwidth is relatively high—especially when multiple units are switched on simultaneously—and so is the processing power required at the desktop.
Almost as expensive and potentially obsolete as a PC, the NC was appealing only to Java zealots, and thus basically doomed at birth. Trying again, Sun recently replaced it with the SunRay, a fascinating device that relies on switched 100Mbit/sec Ethernet connectivity, but, in return, becomes the thinnest possible client.
The SunRay, which has audio capabilities and can drive a 1,280-by-1,024 display, contains only a moderate-performance SPARC CPU and 2Mbytes of main memory. No software is stored or executed on the device; instead, it is run and rendered on a server, then streamed to the SunRay via UDP. User input, such as keystrokes and mouse clicks, is returned to the server in a similar manner.
“This might not be the thin client for you if you primarily want to run Windows applications,” says Gene Banman, Sun vice president and general manager for information appliances. “Going into the future, though, software development should be aimed at Web APIs—and this will be the lowest-cost way to run them. The SunRay ought to be usable for 10 years or more.”
While such devices might inherit the earth, today’s market leader is the Windows-Based Terminal (WBT) architecture developed by Citrix Systems ( http://www.citrix.com/). Citrix has been working on thin clients for 10 years (it released a multiuser version of OS/2 in 1990), and it doubled its user base to more than 15 million in 1999.
