Distributed system is a collection of physically separate, possibly heterogeneous,
computer systems that are networked to provide the users with access to the various
resources that the system maintains. Access to a shared resource increases computation
speed, functionality, data availability, and reliability.
In contrast to the tightly coupled systems, the processors in Distributed Systems do not
share memory or a clock. Instead, each processor has its own local memory and clock.
The processors communicate with one another through various communication lines,
such as high-speed buses or telephone lines within Local Area Network (LAN) or
Metropolitan Area Network (MAN) or Wide Area Network (WAN). These systems are
usually referred to as loosely coupled systems, or distributed systems.
The processors in a distributed system may vary in size and function. They may include
small microprocessors, workstations, minicomputers, and large general-purpose
computer systems. These processors are referred to by a number of different names,
such as sites, nodes, computers, and so on.
Advantages:
• Resource sharing. A user at one site may be able to use the resources available at
another site. For example, a user at site A may be using a laser printer available only at
site B. Meanwhile, a user at B may access a file that resides at A.
• Computation speedup. If a particular computation can be partitioned into a number
of sub computations that can run concurrently, then a distributed system may allow us
to distribute the computation among the various sites — to run that computation
concurrently. In addition, if a particular site is currently overloaded with jobs, some of
them may be moved to other, lightly loaded, sites. This movement of jobs is called load
sharing.
• Reliability. If one site fails in a distributed system, the remaining sites can potentially
continue operating.
• Communication. When many sites are connected to one another by a communication
network, the processes at different sites have the opportunity to exchange information.
Users may initiate file transfers or communicate with one another via electronic mail. A
user can send mail to another user at the same site or at a different site.
computer systems that are networked to provide the users with access to the various
resources that the system maintains. Access to a shared resource increases computation
speed, functionality, data availability, and reliability.
In contrast to the tightly coupled systems, the processors in Distributed Systems do not
share memory or a clock. Instead, each processor has its own local memory and clock.
The processors communicate with one another through various communication lines,
such as high-speed buses or telephone lines within Local Area Network (LAN) or
Metropolitan Area Network (MAN) or Wide Area Network (WAN). These systems are
usually referred to as loosely coupled systems, or distributed systems.
The processors in a distributed system may vary in size and function. They may include
small microprocessors, workstations, minicomputers, and large general-purpose
computer systems. These processors are referred to by a number of different names,
such as sites, nodes, computers, and so on.
Advantages:
• Resource sharing. A user at one site may be able to use the resources available at
another site. For example, a user at site A may be using a laser printer available only at
site B. Meanwhile, a user at B may access a file that resides at A.
• Computation speedup. If a particular computation can be partitioned into a number
of sub computations that can run concurrently, then a distributed system may allow us
to distribute the computation among the various sites — to run that computation
concurrently. In addition, if a particular site is currently overloaded with jobs, some of
them may be moved to other, lightly loaded, sites. This movement of jobs is called load
sharing.
• Reliability. If one site fails in a distributed system, the remaining sites can potentially
continue operating.
• Communication. When many sites are connected to one another by a communication
network, the processes at different sites have the opportunity to exchange information.
Users may initiate file transfers or communicate with one another via electronic mail. A
user can send mail to another user at the same site or at a different site.
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