Thin clients computing

A thin client (sometimes also called a lean client) is a client computer or client software in client-server architecture networks which depends primarily on the central server for processing activities, and mainly focuses on conveying input and output between the user and the remote server. In contrast, a thick or fat client does as much processing as possible and passes only data for communications and storage to the server.

Thus , thin client computing is a server-centric computing model in which the application software, data, and CPU power resides on a network server rather than on the client computer.

A thin client is a network computer without a hard disk drive, which is designed to be especially small so that it does most of its processing on a central server with as little hardware and software as possible at the user's location, and as much as possible at some centralized managed site. Usually, the embedded OS in a thin client is stored in a "flash drive" or in a Disk on Module (DOM). The embedded OS in a thin client usually uses some kind of write filter so that the OS and its configuration cannot been changed but by Administrators.

Advantages of thin clients

Obviously, boot image control is much simpler when only thin clients are used – typically a single boot image can accommodate a very wide range of user needs, and be managed centrally, resulting in:

• Lower IT admin costs. Thin clients are managed almost entirely at the server. The hardware has fewer points of failure and the local environment is highly restricted (and often stateless), providing protection from malware.
• Easier to secure. Thin clients can be designed so that no application data ever resides on the client (it is entirely rendered), centralizing malware protection and minimising the risks of physical data theft.
• Lower hardware costs. Thin client hardware is generally cheaper because it does not contain a disk, application memory, or a powerful processor. They also generally have a longer period before requiring an upgrade or becoming obsolete. The total hardware requirements for a thin client system (including both servers and clients) are usually much lower compared to a system with fat clients. One reason for this is that the hardware is better utilized. A CPU in a fat workstation is idle most of the time. With thin clients, memory can be shared. If several users are running the same application, it only needs to be loaded into RAM once with a central server. With fat clients, each workstation must have its own copy of the program in memory.
• Lower Energy Consumption. Dedicated thin client hardware has much lower energy consumption than thick client PCs. This not only reduces energy costs but may mean that in some cases air-conditioning systems are not required or need not be upgraded which can be a significant cost saving and contribute to achieving energy saving targets.
• Easier hardware failure management. If a thin client fails, a replacement can simply be swapped in while the client is repaired; the user is not inconvenienced because their data is not on the client.
• Worthless to most thieves. Thin client hardware, whether dedicated or simply older hardware that has been repurposed via cascading, is useless outside a client-server environment. Burglars interested in computer equipment have a much harder time fencing thin client hardware (and it is less valuable).
• Hostile Environments. Most devices have no moving parts so can be used in dusty environments without the worry of PC fans clogging up and overheating and burning out the PC.
• Less network bandwidth. Since terminal servers typically reside on the same high-speed network backbone as file servers, most network traffic is confined to the server room. In a fat client environment if you open a 10MB document that's 10MB transferred from the file server to your PC. When you save it that's another 10MB from your PC to the server. When you print it the same happens again – another 10MB over the network to your print server and then 10MB onward to the printer. This is highly inefficient. In a thin client environment only mouse movements, keystrokes and screen updates are transmitted from/to the end user. Over efficient protocols such as ICA or NX this can consume as little as 5 kbit/s bandwidth.
• More efficient use of resources. A typical thick-client will be specified to cope with the maximum load the user needs, which can be inefficient at times when it is not utilised. In contrast, thin clients only use the exact amount of resources required by the current task – in a large network, there is a good probability the load from each user will fluctuate in a different cycle to that of another user (i.e. the peaks of one will more than likely correspond, time-wise, to the troughs of another.
• Simple hardware upgrade path. If the peak resource usage is above a pre-defined limit, it is a relatively simple process to add another rack to a blade server (be it power, processing, storage), boosting resources to exactly the amount required. The existing units can be continued in service alongside the new, whereas a thick client model requires an entire desktop unit be replaced, resulting in down-time for the user, and the problem of disposing of the old unit.
• Lower noise. The aforementioned removal of fans reduces the noise produced by the unit. This can create a more pleasant working environment.
• Less Wasted Hardware. Computer hardware is very environmentally damaging. Thin clients can remain in service longer and ultimately produce less surplus computer hardware than an equivalent thick client installation.