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Corporate Solutions |
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Cash
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Video Surveillance |
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Video Editing |
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Web
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Services |
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| :: File
Server |
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telecommunication, the term file
server has the following meanings:
- A form of disk storage that hosts files
within a network; file servers do not
need to be high-end but must have enough
disk space to incorporate a large amount
of data. Many people mistake file servers
for a high-end storage system, but in
reality, file servers do not need to possess
great power or super fast computer specifications.
- A computer program,
that allows different programs, running
on other computers, to access the files
of that computer.
- In common parlance, the term file
server refers specifically to a computer
on which a user can map or mount
a disk drive or directory
so that the directory appears to be on
the machine at which the user is sitting.
Additionally, on this type of file server,
the user can read or write a file as though
it were part of the file system of the
user's computer.
Files and directories on
the remote computer are usually accessed using
a particular protocol,
such as WebDAV,
SMB, CIFS,
NFS, Appletalk
or their mutations.
- Although files can be sent to and received
from most other computers unless their
primary function is access by the above
means, they are generally not considered
file servers as such.
Memory
requirements
File servers
have historically been instrumental
in pushing up the demand for RAM.
The Novell NetWare
file server operating
system, which dominated the market
for file servers at the time of greatest
growth in demand, read the entire FAT
table into RAM on boot, enabling rapid access to files. Whilst
this guaranteed maximum performance,
it also required large quantities of
memory. This in turn drove demand
for Uninterruptible
Power Supply (UPS) devices as
it became more apparent that power outages
could cause loss of data.
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File and print
Traditionally, file and print services
have been combined on the same computers due to similar
computing requirements for both functions. Usually, such computers
are distinct from application and database servers,
which have different, usually more processor-intensive,
requirements. However, as computing power increases
and file serving requirements remain relatively constant,
it is more common to see these functions combined
on the same machine.
Security
File servers generally offer
some form of system security to limit access
to files to specific users or groups. In large
organizations, this is a task usually delegated
to what is known as directory
services such as Novell's eDirectory
or Microsoft's Active Directory.
These servers work within the
hierarchical computing environment which treat
users, directories, computers, applications
and files as distinct but related entities on
the network and grant access based on user or
group credentials. In many cases, the directory
service spans many file servers, potentially
hundreds for large organizations. In the past,
and in smaller organizations, authentication
can take place directly to the server itself.
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See also
- Backup
- FTP
- Server Message Block
Application
server
An application server is a software engine
that delivers applications to client computers or
devices. Moreover, an application server should
handle most, if not all, of the business
logic and data access
of the application. The main benefits of application
server technology are ease of application development
and centralization.
Although the term application server applies
to all platforms, it has become heavily identified
with the Sun Microsystems J2EE
platform; however, it has also come to encompass
servers of web-based applications, such as integrated
platforms for e-commerce,
content management systems,
affiliate management systems
and occasionally, even applied to simplistic web-site
page builders. The paradigm is more similar to mainframe
based applications than traditional client-server.
Common features
Application server products typically bundle
middleware to enable
applications to intercommunicate with dependent
applications, like web
servers, database
management systems, and chart
programs. Some application servers also provide
an API, making
them operating system
independent.
Portals are a
very common application server mechanism by
which organizations can manage information.
They provide a single point of entry for all
users, they can access Web
services transparently from any device,
and they are highly flexible. Portals can
work inside or outside of the organization,
and they can attach themselves to any part
of it. |
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This term is widely used as a buzzword
in the following fields:
- Distributed computing
— denoting a computer running some part of a distributed
computation task
- Software components
— denoting a "component farm", which is a computer
loaded with software components, ready to answer
calls for usage
- Web services — denoting
a machine running applications which will answer
interface calls over HTTP
in an XML format
History
In the later part of the 1990s,
it was thought that a massive shift over to centrally
served applications was likely, and that the desktop
PC would be replaced by lightweight network
computers. This would have been a return
to the much older model of computing as it was done
in the 1960s, with a
large, very expensive central computer being accessed
by multiple users using dumb
terminals. The difference now was the widespread
use of the graphical user interface
(GUI). Certain products, such as Citrix's
WinFrame, became quite
popular, allowing standard Windows
software to be run on an NT server, and accessed
from a wide variety of clients, including non-Windows
platforms such as Mac
and Unix. Currently,
the trend is to deliver applications via a browser
(see Appaserver) or other
Internet device.
Java application servers
Following the success of the Java
platform, the term application server
sometimes refers to a J2EE
application server. WebLogic
Server (BEA),
JBoss (Red
Hat), WebSphere IBM),
JRun (Adobe)
and Oracle OC4J (Oracle
Corporation) are the better known commercial
J2EE application servers.
GlassFish, an open source
Application Server from Sun, is the first to provide
a robust, commercial, compatible Java EE 5 implementation.
The JOnAS application server,
developed by the ObjectWeb
consortium, is the first non-commercial, open source
application server to have reached the official
certification of compliance
with J2EE. The programming language used is Java.
The web modules are servlets
and JavaServer Pages
(JSP), and business logic is built into Enterprise
JavaBeans (EJB). The Java
2 Platform, Enterprise Edition (J2EE) provides
standards for containing the web components. Tomcat
from Apache and JOnAS
from ObjectWeb are typical of containers to put
these modules into. Both organizations provide the
code freely and openly (open
source).
A JSP is a Servlet from Java that executes in a
web container--the Java equivalent of CGI
scripts. JSPs are a way to create HTML
pages by embedding references to the server logic
within the page. HTML coders and Java programmers
can work side by side by referencing each other's
code from within their own. JavaBeans
are the independent class components of the Java2
architecture from Sun Microsystems.
The application servers mentioned above mainly
serve Web applications. Some application servers
are targeting networks other than the Web. This
is the case of SIP servers,
which target telephony networks.
Other platforms
The term application server has also been
applied to various non-J2EE and non-Java offerings.
For example, with the rising popularity of .NET,
Microsoft can claim to deliver an application server.
Additional open source
and commercial application servers are available
from other vendors. Some examples are Appaserver,
Base4, Concept,
and Zope.
Advantages of application servers
- Data and code integrity
- By centralizing business logic on an individual
or small number of server machines, updates and
upgrades to the application for all users can
be guaranteed. There is no risk of old versions
of the application accessing or manipulating data
in an older, incompatible manner.
- Centralized configuration
- Changes to the application configuration, such
as a move of database server, or system settings,
can be done centrally.
- Security
- A central point through which access to data
and portions of the application itself can be
managed is considered a security benefit, devolving
responsibility for authentication away from the
potentially insecure client layer without exposing
the database layer.
- Performance
- By limiting the network traffic to presentation
layer traffic, it is perceived that the
client-server model improves the performance of
large applications in heavy usage environments.
- Total Cost of Ownership (TCO)
- The above benefits combined are considered to
represent a cost saving to a company. In practice,
however, the technical challenges of writing software
that conforms to that paradigm combined with the
need for software distribution
to distribute client code somewhat negate these
benefits.
See also
- Server
- Client-server
- Standalone server
- Comparison of application
servers See this article for a list of
web application servers listed by programming
language
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