Server is any computer providing
services to other computers, but usually the term server implies a powerful
computer tha supports a number of user simultaneously.
Server
will have a number of features that distinguish it from a desktop computer:
1.
Robustness: the system will be capable of
running 24x7, having higher quality
components and providng reduntdant components.
It means a coponet fail, another is already fitted in the system to take its
place., many configuration operations as possible can take place with out
interrupting services ( hot-swappable for instance).
2.
Scalability: the sysem will be aasily
upgradeable so that it can be improved to meet chaging tequirements. The case
will have plenty of space and connectors to add new components and the power
supply to operate them.
3.
Security: the system will ensure the
intergrity of data by protecting it from system errors, environmental problems,
theft, unauthorised access, and network attachs, such as hacking and viruses.
4.
Performance: the system will user high
performance components such ads the motherboard, processor, meomory and disk
subsystem.
5.
Capacity: the system will provide a large
amount of disk space and backup capability.
Server
are often powerful microcomputers, minicomputers, or mainframes:
Microcomputer: is one based around a
microprocessor (or CPU). Desktop PCs are microcomputers based on the Intel
microprocessor specification(x86). PC Servers are powerful versions of desktop
PCs. PC servers come in a variety of types and specifications, from basic
office file servers to enterprise-levelsystems. Mid- to high-end servers will
incorporate multiple processors( generally 2,4, or 8 ) and multiple gigabytes
of memory. PC servers utilise higher
quality components and greater reliability but also greater cost. PC servers
have more rocessors, memory, disk direves, adapters, and power supplies.
 |
| micro-computer |
Some
of the major manufacturers of PC servers include IBM, HP, Sun, Dell, and Apple.
PC server can run a wide range of Network Operating Systems, including
Microsoft Windows Server, Novel NetWare, Linux and Mac OS X Server.
 |
| Mainframe |
Minicomputer: is a smaller, less powerful, more
affordable version of a mainframe.
Features of Servers:
Features of Servers:
1.
High Availability and Fault
Tolerance: it
is well-known maxim that time costs money. Availability
is not restricted to catastrophic crashes or complete system failures. A system
that is slow is also costing time. Fault
tolerance refers to a server’s
ability to keep serving even if something goes wrong. It is provided through
the robustness of computer components and by providing for redundancy in the system. Where redundancy is provided, the
component is said to be n+1, where n is the number of components in use and 1
is a spare to be used in the event of failure.
2.
Clustering: a clustering services is a means of providng redundancy to protect
access in the event of hardware failure. A cluster consists of nodes; each a
separate server providing duplicate services. In the event of a failure, the
remain nodes will take on the services of failed node.
3.
Load Balancing: refers to distributing requests
between multiple components. From the point of view of the client, there is
noly one resource. In some configurations, having multiple components can
provide load balancing and redundancy. Other load balancing configurations do
not provide redundancy; if one component fails, the whole system goes down.
4.
Scalability: means the ability to improve the
performace of a server without diminishing its usefulness or increasing tis
cost disproportionately. A well-designed server is able to expand to meet the
increased needs of its users.
Operating systems for Server:
Server
can run a wide ranger of network operating system (NOS) such as Microsoft
Windows Server, Novel NetWare, Linux and Mac OS X Server. The main areas that
should be considered when selecting a NOS are as follows:
§ Performance:
produce
adequate throughput and response for the desired number of users and does it
support adequate storadge? Most NOS support multiprocessing. An NOS also often
supports more memory than desktop OS.
§
Reliability: assurance that the system run
24x7 and provide fault tolerance.
§
Scalability: is it capable of being scaled-up
as the network grows (maximum number of users supportd) ? NOS also support
features such as clustering and load balancing.
§
Security: does it provide adequate
protection for data?
§
Platforms available: compter architures that can be
used.
§
Management: it should provide powerful and
non-complex tools to centrally manage the network.
§
Interoperability: ability to work with other
systems.
§
Application support: what applications are available?
§ Cost
per user: how
does the system compare with its competitors when the above factors are
considered?
Types of servers:
These
services may run on a dedicated server or you may coinfigure a single box to
run multiple services, depending on the size of the network and budget.
Network services
·
Directory services and
authentication: the
network is controlled by an administrator by specifying accounts on a directory
server. In order to use the network, a user must be authenticated by supplying
a correc username and password at log on. Additional security can be enforced
by requiring other authentication, such as swiping a smartcard… To access a
resource on the network, the user must also have been granted the appropriate
permissions. Permissions are applied to group accounts, and then users are
assigned to one or more group accounts. Most directory services are
implementations of the Leghtweight Directory Access Protocol(LDAP).
·
Network configuration and access:
many
server are configured to provide addressing information on a network, running
TCP/IP services such as DHCP, DNS and WINS. They may also be configured to
function as a firewall, proxy server, a gateway, router, or bridge. They can
also be configured to provide remote access to resources on server (VPN).
·
Network monitoring: the server can be configured to
monitor the network and collect infromation about assets.
File and Print Services: one of the basic functions of a
server is to provide shared access to folders and files. This has severa
advantages:
·
More
disk space is made available to users cheaply.
·
File
version control can be administered centrally
·
Files
can be secured against unauthorised access.
·
Data
can be backed up more reliably.
·
A
print server enables multiple users to use a print device saving on costs
Internet services: A server connected to the
internet can function as a web server.
·
Applications: Typical server application
include email, groupware, databases, accounting…As applications can be
demanding to run, they are often located on dedicated applicaion servers.
·
Dedicated Application: the term refers to server hardware
that runs one application only. The application gets reliable performance from
server hardware. But higher cost in terms of providing dedicated equipment.
·
Distributed Application: is provided by more than one
physical server on the network. Data can be distributed around thes servers.
This model provides robustness. Services are not generally interrupted because
of the failure of individual services. It can also improve performance by
distributing load between different machines.
·
Peer-to-Peer Application (P2P): each instance of the application
can act as both client and server to other instances. P2P applications are
capable of utilising spare capacity from all nodes to improve performance.
Planning server:
In
planning a server network, the following questions are important:
·
What
services(applications) and /or resouces (disk space, print facilities, and so
on) must be provided to network users?
·
What
load is to be expected for each application and resource? ( how many
simultaneous users the server would support and capacity require)
·
What
growth ca the network expect in the future?
The
answers to these questions determine how you specify your server system.
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