Warm up group6

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Execution Environments for Distributed Computing Distributed Systems EEDC 3 4 3 3 0 Master in Computer Architecture, Networks and Systems - CANS Homework number: 6 Group number: EEDC-1 Group members: Umit Cavus Buyuksahin Ziwei Chen Faik Aras Tarhan {umit.cavus.buyuksahin, zwei.chen, faik. aras.tarhan}@ac.upc.edu

Transcript of Warm up group6

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Execution Environments for Distributed Computing

Distributed Systems

EEDC 34330

Master in Computer Architecture, Networks and Systems - CANS

Homework number: 6Group number: EEDC-1

Group members:Umit Cavus Buyuksahin

Ziwei ChenFaik Aras Tarhan

{umit.cavus.buyuksahin, zwei.chen, faik.aras.tarhan}@ac.upc.edu

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OUTLINE

● Concepts of Distributed System○ Definition ○ Brief history○ Goals○ Architecture

● Centralized & Decentralized Systems● Differences from centralized & decentralized systems

○ Differences from centralized system○ Differences from decentralized system

● Examples● Conclusion

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Definition

● A distributed system is a piece of software that ensures that: a collection of independent computers appears to its users as a single coherent system.

● Two aspects: (1) Independent computers and (2) single system => middleware.

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Brief history

● 1945 ~ 1985○ ... computers were large and expensive○ ... no way to connect them○ ... all systems were Centralized Systems.

● Mid 1980s○ ... powerful microprocessors.○ ... high Speed Computer Networks (LANs, WANs).

● Then Distributed System came

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Goals

● Resource Sharing○ ... with Distributed Systems, it is easier for users to access remote resources

and to share resources with other users.● Openness

○ ... the openness of DS is determined primarily by the degree to which new resource-sharing services can be added and be made available for use by a variety of client programs.

● Transparency○ ... it hides the fact that the processes and resources are physically distributed

across multiple computers.● Scalability

○ ... a system is described as scalable if it remains effective when there is a significant increase in the number of resources and the number of users.

● Concurrency ○ ... there is a possibility that several clients will attempt to access a

shared resource at the same time.

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Architecture

A distributed system organized as middlewareThe middleware layer extends over multiple machines, and

offers each application the same interface.

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Centralized & Decentralized Systems

● Centralized Systems○ ... designed around a central

workstation

(+) simple and ease to maintain (-) non-scalable, single point of failure

● Decentralized Systems○ ... have exact opposite

characteristics of centralized sys.

(+) self-regulating, faster decision, scalability (-) difficult to manage

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Differences From Centralized Systems

● Concurrency ... runs in concurrent processes on different processors

● Authority ... gives less authority to make decision

● Interaction ... more interaction between parts of organization

● Applicability ... best-suited to large industries and companies

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Differences From Centralized Systems

● Communication ... from top to bottom, bottom to top as well as across

● Points of Control ... multiple points of control

● Points of Failure ... multiple points of failure

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Differences From Decentralized Systems

● The difference is subtle.● The terms are probably used more or less interchangeably by

many.

● Decentralized systems ○ ...not necessarily 'distributed'○ ... does not have spread of functionality○ ... less resilient

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Examples

● The world wide web – information, resource sharing● Clusters, Network of workstations● It is easier for users to access remote resources and to

share resources with other users like○ printers, files, Web pages, etc

● Distributed manufacturing system (e.g., automated assembly line)

● Network of branch office computers - Information system to handle automatic processing of orders

● Network of embedded systems● New Cell processor (PlayStation 3)

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Examples - Internet

● The Internet is a vast interconnected collection of computer networks of many different types. [Coulouris et al, p.3]

● World’s largest client/server application

● Giant virtual disk

● Giant hyperlinked document

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Examples - Centralized & Decentralized

● Napster○ on startup, client contacts central server○ reports list of files to central server○ return someone that stores the requested file○ get the file directly from peer

● BitTorrent○ run a tracker server to publish ○ contact centralized “tracker”

server, get a list of peers

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Examples - Centralized & Decentralized

● Gnutella○ fully decentralized○ search cost distributed

● FreeNet

● KaZaA○ no dedicated server○ not all peers are equal○ on startup, client contacts a “supernode” ○ send query to supernode, supernodes flood query

among themselves

● DHTs

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References

● http://www.cis.upenn.edu/~lee/07cis505/Lec/lec-ch1-DistSys-v4.pdf

● http://www.linkedin.com/answers/management/planning/MGM_PLN/212509-5526887

● http://www.cs.ucl.ac.uk/staff/ucacwxe/lectures/ds98-99/dsee3.pdf

● http://www.ehow.com/info_10037010_difference-between-centralized-distributed-management-system.html

● http://openp2p.com/pub/a/p2p/2002/01/08/p2p_topologies_pt2.html