Distributed Computing System Learning Essays Chapter I Introduction

1.1

1. Two major technologies to promote the development of distributed computing systems:

1) Development of computer hardware technology and software technology

2) Development of computer network technology

1.2

1. What is a distributed computing system?

A distributed computing system consists of several interconnected processing resources, which can cooperate to perform a common task under the control of the whole systems, and at least rely on centralized program, data and hardware. These processing resources can be physically contiguous or geographically dispersed.

2. Description of the definition of distributed computing system

1) The system is made up of multiple processors or computer systems

2) Two types of structure: these computing resources can be physically adjacent, by the machine internal bus or switch connected to the processor, through the sharing of main memory to communicate; These computing resources can also be geographically separated, by the computer Communication Network (remote network or LAN) connected to the system, the use of messages to communicate.

3) These resources form a whole and are transparent to the user, that is, users do not need to know where to use any of the resources.

4) A program can be dispersed across the computing resources to run.

5) The status of each computing system is equal, except under the control of operating system, there is no master-slave control and centralized control link.

3. Tightly coupled and loosely coupled distributed computing systems

	Tightly coupled distributed computing system	Loosely coupled distributed computing system
Connection mode	Internal bus or in-machine interconnect network	Communication network
Process resource distance between resources	Physically dispersed, very close to each other.	Geographically dispersed, far apart
Working with resources	Processor	Computer
Communication mode	Shared memory	Message exchange

1.3

1. Advantages of Distributed Computing system

1) scalability, 2) high performance/price ratio; 3) resource sharing, 4) reliability, 5) support for inherently distributed applications.

1.4

1, transparency: things have a certain property, but this property from a certain point of view is not visible, called this characteristic is transparent.

2, the transparency of distributed computing system: The user or programmer cannot see the existence of the network. This way, from the user or programmer's point of view, all the machines in the network behave as one, and the user or programmer cannot see the boundaries of the machine and the network itself. Users do not have to know where the data is placed and where the process is executing.

3. Transparency of distributed computing systems:

1) name transparency: refers to the name of the object in the global is unique, regardless of where access to the object used by the names are the same. In this way, moving a program in the system does not affect its correctness.

2) Location Transparency: refers to the resource's name that does not contain the location information for the resource. In this way, when the resource is moved in the system, the original program can run normally if the resource name remains the same.

3) Access transparent: Users do not have to differentiate between local and remote resources, and the same approach to accessing local resources and accessing remote resources.

4) Migration transparency: Refers to the user does not know a resource or whether his job is migrated to another location. Migration transparency requires name-transparent support.

5) Replication transparency: Allow multiple copies of a file or other object to exist on the system at the same time, but this is transparent to the user, and modifications to the object should be applied to all copies of the object at the same time.

6) Concurrency and parallel transparency: multiple processes may access the same resource concurrently or in parallel, or a process can use multiple resources at the same time, in which case there is no mutual interference and corruption.

7) Failure Transparent: When a part of the system fails, the whole system will not fail, and still can operate normally.

Distributed Computing System Learning Essays Chapter I Introduction