Thin
Client, Server Based Computing, Network Computing
A
thin
client is a simple client
program or hardware device which depends primarily on the
central
server for processing activities because it has little
or no application logic. In contrast to a thick or fat client,
which does as much processing as possible and passes only
data required for communications and archival storage to
the server,
a thin
client is a network computer without a hard disk drive,
which, in client/server
applications, is designed to be especially small so that
the bulk of the data processing occurs on the server.
The word "thin" refers to the small boot image
which such clients
typically require.
When
designing a client-server
application, the decision as to which parts of the task
should be done on the thin
client, and which on the server
can crucially affect the cost of thin
client and servers,
the force and security of the application as a whole, and
the flexibility of the design to later modification or porting.
How
application-specific the client
software should be is another question. Using standardized
thin
client software
such as a Web browser or X11 display can save on development
costs, since one does not need to develop a custom client—but
one must accept the limitations of the standard client.
Application
Program
A
thin
client as an application program communicates with an
application
server, relying on a separate piece of software for
the most significant elements of its business logic. A thin
client does most of its processing at the central
server based computer (server
based computing), the thin
client with as little hardware and software as possible,
and as much as possible at some centralized managed site.
However,
a great deal of software
today is typically included in the base boot image of a
thin
client, specifically to support various user applications
running at the server
based computing , so that it need not be reinstalled
on every computer. Often, a departmental boot image is prepared
to include applications specific to a department.
User-Interface
Device
The
thin
client device is specifically designed to provide just
those functions which are useful for user-interface programs.
Because they may become corrupted by the installation of
misbehaved or incompatible software, often such devices
do not include hard disk drives. But instead, in the interests
of low maintenance cost and increased mean-time between
failures, the thin
client device will use read-only storage such as a CD-ROM,
Network Virtual Drive, or flash memory. The user will have
only a screen, a keyboard, a pointing device (if needed),
and enough computer to handle display and communications.
Thin
Client Software
Most
thin
clients are software-only and run on standard PC hardware.
One example of this software-only thin
client is Applica ThinWorks,
a smaller thin
client on the market, running in conjuction with ApplicaServer
and offering the best solution in network computing. ThinWorks
offers UXVGA graphics ports, with usb and audio, capable
of running real time movies from the ApplicaServer.
The system is based on RDP protocol and represents the best
remote desktop available in the maket. ApplicaServer
thin
computing from Applica offers the total solutions to
run multiple thin
client remote desktops on Windows XP.
Examples
of Thin Client and Thick Client Usage
A
few situations may clearly call for one or the other two
approaches. Distributed computing projects such as the big
offices (whose whole point is to pass off computationally
intensive analysis to a large collection of remote computers)
are applications that require thick clients. On the other
hand multicasting entertainment or educational material
to a number of clients
might best be done with thin
clients since exactly the same material is to be presented
at each.
Some
technologies such as Network Virtual Disks or Disk Drive
Images are aimed to provide central management and security/reliability/affordability
comparable to what is found in thin
client devices: the OS that operates the client
is stored on a shared virtual disk image (a disk image file)
that is housed on a server
in the clients'
LAN. This virtual disk drive is "write protected"
and shared by several clients
at the same time. The content of this virtual disk drive
is streamed on demand to the clients.
Yet, all the computing is done by the client
itself. Instead of centralizing a complete computer (centralize
the storage, CPU, memory, devices etc) this approach centralizes
only the hard disk drives. Because the virtual disk drives
can be shared and protected, the aim to reduce TCO is also
achieved with this technology. This technology can be used
to run typical Embedded Operating Systems such as Embedded
Linux and Windows XP Embedded, but also to run desktop operating
systems such as Microsoft Windows XP Pro, FreeBSD or Linux.
Organizations that develop and market Network Virtual Disks
include Linux Terminal Server Project, IBM (iBoot technology).
Network ffBlock Device support is another kind of Network
Virtual Disk embedded in Linux.
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
client can be designed so that no application data ever
resides on the client
(it is entirely rendered), centralizing malware protection.
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) is 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 enery 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.
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 file server
and another 10MB back 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 this can consume as
little as 5Kbps bandwidth.
Advantages
of Thick Clients
Fewer
Server Requirements - A
thick client server does not require as high a level of
performance as a thin
client server (since the thick clients themselves do
much of the application processing). This results in drastically
cheaper
servers.
Better
Multimedia Performance - Thick clients have
advantages in multimedia-rich applications that would be
bandwidth intensive if fully served. For example, thick
clients are well suited for video gaming.
More
flexibility - On some
operating systems (such as Microsoft Windows) software products
are designed for personal computers that have their own
local resources. Trying to run this software in a thin
client environment can be difficult.
Summary
A
thin
client PC is a PC coupled with software to make it look
and function like a standard thin
client. Thin
client PCs provide all the advantages of thin
clients such as ease-of-management, reliability and
increased control while avoiding the known limitations associated
with typical thin-client
devices. The thin
client PC solution is secure by definition and can support
environments that need the locked-down desktop control while
still maintaining the flexibility of a PC for local application
and I/O support.
The
thin
client PC solution is perfect for all organizations
that require a full-function local Internet browser, local
applications and want to access the proven benefits of server-based
computing such as greater control, scalability and cost
containment. IT teams also find this solution ideal for
terminal replacement or kiosks projects, which can be implemented
prior to investing in Microsoft Terminal Services or Citrix
MetaFrame.
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