Pros and Cons of Terminal-based Rooms

Lukáš Slánský, Tomáš Hudec Institute of Electrical Engineering and Informatics, University of Pardubice [email protected], [email protected]

Abstract printers. In late 1970s were introduced “intelligent” terminals, such as VT52 or VT100 made by DEC1. These Maintenance of computer rooms is for administrators were called “intelligent” because they had the ability of very time consuming job. It is caused by the number of positioning and control the display. that are needed to administer—its hardware In 1981 IBM presented their IBM-PC computer that in could fail, OS and applications must be installed, later years began pushing out the solutions. In maintained and keep secure. 1980s and 1990s were PCs virtually on every desktop and However it is possible to use centralised solution using computer terminals were used only for accessing the thin clients. Its benefits are mainly centralised servers and mainframes. In this case were terminals used administration (all maintenance work is done only on few mainly as virtual terminals—computer programs that servers), fail safety (terminals have no moving parts), connects to server over network and uses clients’ flexibility (terminals could be connected just plug & play) keyboard and display to communicate with user. The real and power consumption (terminal has typical computer terminals were almost extinct. consumption about 4 W—98 % compared to typical Since introducing X11 protocol in 1987 were PC). graphical terminals used. The X11 protocol allows This solution has also its drawback—it is dependent on transporting graphical instructions to terminals and working network and servers, primary investment to keyboard and mouse events back. In early times was X11 servers is high and others. used mainly for local access and for remote access to servers from PCs through LAN. Graphical terminals are nowadays called as “thin clients” 1. Computer terminals and are mostly graphical. Typical thin uses X11 protocol for accessing UNIX or Unix-like systems and Computer terminal (1) is an electronic device that is used since introducing Windows NT 4.0 , for entering data into, and displaying data from, a released in 1998, RDP protocol for accessing Windows. computer or a computer system. It is consisting of a video Terminals (thin and thick2 clients) are in modern adapter, a monitor, and a keyboard. The adapter and infrastructure used more and more. Reasons for using monitor and sometimes, although less commonly, the terminals and reasons against that are described below in keyboard are usually combined in one unit. A terminal chapters Chyba! Nenalezen zdroj odkazů. and Chyba! does little or no computer processing on its own; instead, Nenalezen zdroj odkazů.. it is connected to a computer with a communications link over a cable. Keyboard input is sent from the terminal to the computer; video output is sent from the computer to 2. Advantages of terminal-based computer the terminal. Terminals are used primarily in multiuser rooms systems and today are not often found on single-user personal computers. Thin clients have many advantages compared to personal computers. These units are very cheap—much cheaper 1.1. History of computer terminals than real PCs. Yes, you must invest to server but in overall from the certain number of terminal clients the In 1970s were computers generally large (2), costly amount of the spent money per working place is lower. systems owned by large corporations, universities, For administrators it is also easiest job to maintain one or government agencies and similar-sized institutions. End two servers and no workstation at all than a room full of users often did not directly interact with the machine but PCs. Not only installation of software can be done only instead would prepare tasks for the computer on off-line once but also increasing terminal count is easy. With real equipment. thin clients one has to only unpack a terminal, connect it A more interactive form of computer use was time- sharing system, where multiple computer terminals let 1 These terminals are still widely emulated in software to many people share the use of one connect to servers through or SSH. processor. This was common in business applications and 2 Thick clients are diskless computers with some basic OS in science and engineering. In these times were terminal that can download applications from server and run that capable displaying only text information—just like locally. to power supply, network, monitor, keyboard and mouse Beside the advantages there are also some disadvantages. and then only switch it on. No more installation, no more The most notable is the centralisation. All configuration works, no BIOS setup, no replacing non- power is centralised to one place. If this computer fails, working HW components. all terminals are useless. That's why these systems must A PC-based computer room will come one time outdated. be reliable. This has also an impact on their cost. All PCs should be at least upgraded or even replaced by Moreover their computing power serves many terminals new, more powerful models. This is neither cheap nor and users. This is another good reason for investing to easily done. The administrator has to install new good, reliable, scalable server. components to all the PC units or—when replacing whole The central server is the most important part and can be PCs—reinstall , drivers and applications. expensive. To eliminate possible failure of the server it is This all one by one PC which is also time consuming. good to invest in some UPSs4 for it and possibly in a On the other hand with terminal based computer room if backup server. This investment can save money in the the server runs out of resources with increasing number of future because it nearly eliminates risk of nonworking clients one has to strengthen only the server (in memory system. Along with investment to server part it is wise to or possibly in number of CPUs) or even double it by have reliable and fast network equipment. All buying second server (which will also make the system computational work is done by server and the user at more robust). Installation of a new server is easier terminal only enters commands and can sees results. If because it can often be almost identical clone of the first this is all user expects everything is okay. But if you think one. Upgrading computing power is therefore easier with about graphical programs which require lots of video data terminal based solutions. to be displayed or sound applications there is a need to Other advantages include also quiet working conditions. transfer data from server to a terminal unit at relatively With PCs you can hear coolers of power supply units, high speed. Network traffic can increase in these CPUs and sometimes GPUs3 and chipsets. In a computer circumstances. room it is significantly less of noise or even none at all. For a small computer room it is possibly cheaper to have Terminals also do not emit a heat so air conditioning is real PCs, but if one plans to increase number of not needed. workstations or even computer rooms then terminal based Real terminals are also stateless piece of hardware. This solution is a really good choice. means that one can turn it off and on back again and user working session is restored as it was. Applications including the session run on a server and this make thin 4. Sun Rays at University of Pardubice clients also resistant to power failures in a computer room. Short power failure will cause no more working Sun Ray thin clients enable all computing to be done break than logging on back to the still existing session remotely. They represent the first successful with all application windows open in the same state they implementation of true thin-client computing (3), and they were before the failure. Server is often powered by run on multiple hardware and software platforms, backup power source so no work is lost. including three popular variants as well as the This statelessness feature of terminal based solutions can extremely stable and reliable Solaris Operating System. 5 be extended to moving sessions between thin clients. One Compared to other devices, Sun Ray DTUs have a can log in and work in his/her own room and then detach moderate cost of acquisition and a very low total cost of and reattach on any other terminal in another room. ownership because, once acquired, they do not have to be Process accounting applications are also much easier to replaced and never require local software upgrades or write because they run on the same server as user's desktop system administration. application which is taken into account. Various models of Sun Ray DTUs are available, differing In a PC-based computer room with only a few users primarily with respect to size and of screen. All Sun working all the computing power of other PCs is Ray DTUs include a smart card reader, a keyboard, and a unutilised. The user cannot make use of other PCs mouse. Sun Ray DTUs have no local disks, operating computing power. This is different with thin clients. If systems, or applications; they are therefore considered user applications run on the server he/she can make use of stateless. Statelessness is what makes thin clients thin. It all computing power of the idle server. If there are only also helps to make them secure and easy to maintain. For few users working they can use more computing power instance, although USB mass storage devices are for their purposes than on a single PC. supported, the ability to use them is administered centrally. So sites with security requirements can easily disable their use to remove the sort of risk imposed by 3. Disadvantages of terminal-based PCs and other fat clients that permit or even encourage computer rooms the loss of data in case a physical device is stolen. In a typical Sun Ray implementation, the smart card can serve as a company ID/electronic door key, government

4 UPS—Uninterruptible Power Supply 3 GPU—Graphical Processor Unit 5 DTU—Desk-Top Unit Common Access Card, or a student ID card. Like an ATM card, the card itself is protected from unauthorized use by a password or PIN. The card can be configured to contain other applications and information, such as security permission levels, as well.

4.1. Conclusion

Terminals in computer-rooms are good solution in general. Advantages of this solution outweigh the disadvantages. Main advantages of terminals: Easy administration and maintenance (especially software installation). Ease of upgrading computing power. Low cost of acquisition new units. Low cost of ownership (low power consumption, no need of HW upgrades). Statelessness of the thin clients and roaming sessions. Better utilisation of the CPU power. Disadvantages of terminals: Centralisation threats accessibility of terminals. Network dependency and consumption. Expensive servers. In Institute of Electrical Engineering and Informatics are used Sun Ray clients as terminals. Till now we have used terminals for courses concerning programming and operating systems. In future we plan upgrading terminal server software to fulfils all needs that are important for all-purpose computer-rooms—especially the possibility to run Windows applications such as MS Office, MS Visual Studio or AutoCAD.

5. Bibliography

1. Computer terminal. Wikipedia, the free encyclopedia. [Online] 2 Nov 2007. [Cited: 9 Nov 2007.] http://en.wikipedia.org/wiki/Computer_terminal.

2. . Wikipedia, the free encyclopedia. [Online] 7 Nov 2007. [Cited: 9 Nov 2007.] http://en.wikipedia.org/wiki/Personal_computer.

3. Sun Microsystems, Inc. Sun Ray Overview White Paper. [Online] Dec 2004. [Cited: 9 Nov 2007.] http://www.sun.com/sunray/techinfo/New_SR_WP_12_0 4.pdf.

4. Computer terminal. Wikipedia, the free encyclopedia. [Online] 2 Nov 2007. [Cited: 9 Nov 2007.] http://en.wikipedia.org/wiki/Computer_terminal.