Servers
In information technology, a server (also called a server application) is "an
application program that accepts connections in order to service requests by
sending back responses." (RFC 2616 (Hypertext Transfer Protocol -- HTTP/1.1)) A
server application can run on the same
computer as the
client application using it, or they can connect through a
computer
network. Examples include file server, database server, backup server, print
server, mail server, web server, FTP server, application server, VPN server,
DHCP server, DNS server, WINS server, logon server, security server, domain
controller, backup domain controller, proxy server, firewall, etc.
Server is an adjective in the term server
operating system.
A server operating
system is intended, enabled, or better able to run server
applications. The
differences between the server version and the "workstation"
version of an operating system vary. Sometimes (as in the case of Windows 2000
and Windows 2000 Server), the primary difference is the removal of arbitrary
license-dependent limits on the number of
network
file share connections accepted. Some server editions include additional server
applications bundled with the operating system. Some server applications (e.g.
Microsoft IIS) impose arbitrary limits on the number of HTTP connections they
will accept, depending on whether they are running under a server operating
system or not.
A server computer
(often called server for short) is a
computer system
that has been designated for running a specific server
application or
applications. A
computer that is designated for only one server
application is
often named for that
application. For example, when Apache HTTP Server (software)
is a company's web server, the
computer running
it is also called the web server.
Server applications
can be divided among server
computers over
an extreme range, depending upon the workload. Under light loading, every server
application can run concurrently on a single
computer. Under
heavy loading, multiple server
computers may be
required for each
application. Under medium loading, it is common to use one server
computer per
server application,
in order to limit the amount of damage caused by failure of any single server
computer or
security breach of any single server
application. Any
server computer
can also be used as a
workstation, but
it is avoided in practice, again to contain risk.
Server or server
computer is also a designation for
computer models
intended for use running server
applications,
often under heavy workloads, unattended, for extended time. While any "workstation"
computer can run
server operating
systems and server
applications, a
server computer
usually has special features intended to make it more suitable. Distinctions
often include faster
processor and
memory, more RAM,
larger hard
drives, higher reliability, redundant
power supplies,
redundant hard
drives (RAID), compact size and shape, modular design (e.g., blade servers
often used in server farms),
rack or cabinet
mountability, serial console redirection, etc.
The name server or server appliance also applies to network-connected
computer
appliances or "appliance hardware" that provides specific services onto the
network.
Though the appliance is a server
computer, loaded
with a server
operating system and a server
application, the
user need not configure any of it. It is a black box that does a specific job.
The simplest servers are most often sold as appliances, for example switches,
routers, gateways, print servers, net modems.
|
