Showing posts with label operating systems. Show all posts
Tuesday, 12 February 2019
Distributed OS or Distributed Systems (also called loosely coupled systems)
on
February 12, 2019
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.
Monday, 11 February 2019
Different types of Operating system
multiprocessor operating systems
operating systems
Parallel system
Multiprocessor systems or Parallel Systems (also called tightly coupled systems)
on
February 11, 2019
Multiprocessor Operating System refers to the use of two or more central processing
units (CPU) within a single computer system. These multiple CPUs are in a close
communication sharing the computer bus, memory and other peripheral devices.
Multiprocessor systems are also called as parallel systems or tightly coupled systems.
These types of systems are used when very high speed is required to process a large
volume of data. These systems are generally used in environment like satellite control,
weather forecasting etc.
Advantages:
Increased Throughput: By increasing the number of processors, we expect to get more
work done in less time.
Economy of scale: Multiprocessor systems can cost less than equivalent multiple single-
processor systems, because they can share peripherals, mass storage, and power
supplies.
Increased reliability: As there are multiple processors in the system, failure of one
processor will not halt the system, only slow it down. This ability to continue providing
services proportional to the level of surviving hardware is called as graceful
degradation.
Disadvantages:
Multiprocessing can cause a system to change its memory access model from uniform
memory access (UMA) to non-uniform memory access (NUMA). NUMA is a kind of
situation in which some parts of memory may take longer to access than other parts
creating a performance penalty.
Types of multiprocessor systems:
There are two types: multiprocessor systems using asymmetric multiprocessing (ASMP)
and multiprocessor systems using symmetric multiprocessing (SMP).
In ASMP each processor is assigned a specific task. There is one master processor which
controls the system and the other processors are the slave processors. The master
processor allocates and schedules the work to the slave processors. Slave processors
perform the task given to them by master processor.
In SMP no master-slave relationship exists between processors. Each processor has its
own set of registers as well as local cache. All the processors share the same physical
memory and all of them run an identical copy of operating system
units (CPU) within a single computer system. These multiple CPUs are in a close
communication sharing the computer bus, memory and other peripheral devices.
Multiprocessor systems are also called as parallel systems or tightly coupled systems.
These types of systems are used when very high speed is required to process a large
volume of data. These systems are generally used in environment like satellite control,
weather forecasting etc.
Advantages:
Increased Throughput: By increasing the number of processors, we expect to get more
work done in less time.
Economy of scale: Multiprocessor systems can cost less than equivalent multiple single-
processor systems, because they can share peripherals, mass storage, and power
supplies.
Increased reliability: As there are multiple processors in the system, failure of one
processor will not halt the system, only slow it down. This ability to continue providing
services proportional to the level of surviving hardware is called as graceful
degradation.
Disadvantages:
Multiprocessing can cause a system to change its memory access model from uniform
memory access (UMA) to non-uniform memory access (NUMA). NUMA is a kind of
situation in which some parts of memory may take longer to access than other parts
creating a performance penalty.
Types of multiprocessor systems:
There are two types: multiprocessor systems using asymmetric multiprocessing (ASMP)
and multiprocessor systems using symmetric multiprocessing (SMP).
In ASMP each processor is assigned a specific task. There is one master processor which
controls the system and the other processors are the slave processors. The master
processor allocates and schedules the work to the slave processors. Slave processors
perform the task given to them by master processor.
In SMP no master-slave relationship exists between processors. Each processor has its
own set of registers as well as local cache. All the processors share the same physical
memory and all of them run an identical copy of operating system
Subscribe to:
Posts
(
Atom
)
