System Architecture & Hardware Configurations Dr. D. Bilal IS 582 Spring 2007.

System Architecture & Hardware ConfigurationsDr. D. Bilal

IS 582

Spring 2007

System Architecture

Two major system architectures:HierarchicalClient/Server

Hierarchical Architecture

Processing and activities are controlled by the host system

Remote computers connected to host system have limited functions

(input/output)

Hierarchical Architecture

Remote computers connected to the host system emulate “dumb” terminals in communicating with the host system.

“Dumb” terminals have no or limited processing capabilities.

Client/Server Architecture

Client: a user’s computer Server: a dedicated computer in a

network shared by multiple users More than one server can exist in this

architecture (e.g., database server, Web server, application server, e-mail server)

Client/Server Architecture

A computing architecture in a LAN or WAN environmentClients on network perform certain

processing functions when requesting information from a server in the network

Client/Server Architecture

TCP/IP to establish communications between clients and servers

Clients handle the user interface screen formatting, display of results,

input/outputmake requests and send them to the

application server

Client/Server Architecture

Server searches for requested information and sends results to the client(s)

Server performs database management, information retrieval, transaction and processing tasks.

Server delivers access to files, applications, and network communications.

File Server Architecture

User requests information from a server Entire database file is downloaded in the

computer making the request results in slow communication between the

user’s computer and the server.

File Server Architecture

Software programs are loaded onto the server only.

Installing updates are done in server Updates take less time to install than

those in client/server architecture

Client/Server Architecture

One client may connect to one or more servers: OPAC server, T-mail server, and other servers

One server may connect to multiple clients concurrently.

Client/Server Architecture

Each client that is connected in a client/server network must have part of the automation software (e.g., user interface) loaded into the computer

(hard disk) that allows it to perform certain application tasks.

Client/Server Architecture

If all OPACs in a network must have access to the Web, all clients must have a Web browser.

If all clients must provide access to e-mail, they must have the e-mail client software loaded on them.

Client/Server Architecture

Servers may be large scale computers, mid-range computers, or high speed microcomputers.

True client/server means that the application was originally designed to run on a network (LAN or WAN).

Client’s Functions/Tasks

Handles the user interface. Translates the user's request into the

desired protocol. Sends the request to the server. Wait for the server's response. Present the results to the user.

Server’s Functions/Tasks

Receives a request/query from the client.

Processes the query. Returns the results back to the

client. Client presents the results to the

user.

Two-Tier

Server: Processes database tasks such as search and retrieval.

Client: Processes application tasks. A request is generated in the client and

transmitted to the server. The Database Management System that

resides on the server searches for the desired information and transmits the results of the request to the client.

The client present the information to the user on the screen.

Three-Tier

Used when applications are in high demand.

An additional server is used for application processing tasks.

Both the client and the additional server perform application processing tasks.

The other server performs the database management tasks (searching, retrieval, etc.).

Types of Client/Server: Thin Clients

Computer terminals rather than desktop computers.

Do little or no data processing tasks. Process information (input/output). Used to lower PCs and Macs cost

used in a network.

Types of Client/Server: Thin Clients

May be used as e-mail stations, Web access stations, and/or OPACs stations.

Can co-exist with thick or fat clients in a network.

Client/Server Architecture

Benefits See Bilal, 2002, pp. 33-34.

Disadvantages See Bilal, 2002, p. 34.

Additional information is found at: http://www.sei.cmu.edu/str/descriptions/client

server.html http://www.answers.com/topic/client-server

Options for Hardware Configurations

Non-networked (a.k.a. stand-alone)AdvantagesDisadvantages

Difference between stand-alone hardware configuration and stand-alone software configuration.

Options for Hardware Configurations

Networked: LAN-basedAdvantagesDisadvantages

Networked: WAN-basedAdvantages Disadvantages