1-intro_zy 分布式计算简介.ppt

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分布式计算系统puting Systems
赵洋(@)
南京理工大学计算机学院
2010年秋季学期
本课件来源于Jennifer Welch教授Distributed Algorithms and Systems(CPSC 668)课程
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教材: 《分布式计算(第二版)》,puting: Fundamentals, Simulations and Advanced Topics (2nd Edition).
Hagit Attiya,Jennifer Welch 著
骆志刚等译
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Distributed Systems
A distributed system is a collection of puting devices that municate with each other.
Distributed systems have e ubiquitous:
share resources (computation, storage…)
communicate (www, email, p2p)
increase performance
speed
fault tolerance
Characterized by
independent activities (concurrency)
loosely coupled parallelism (heterogeneity)
inherent uncertainty
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Uncertainty in DS
es from
differing processor speeds
puter architectures
munication delays
(partial) failures
multiple input streams and interactive behavior
multiple users
human intrusion
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Reasoning about DS
Uncertainty makes it hard to be confident that system is correct
To address this difficulty:
identify and abstract fundamental problems
state problems precisely
design algorithms to solve problems
prove correctness of algorithms
plexity of algorithms (., time, space, messages)
prove impossibility results and lower bounds
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Potential Payoff of Theoretical Paradigm
careful specifications clarify intent
increased confidence in correctness
if abstracted well then results are relevant in multiple situations
indicate inherent limitations
cf. pleteness
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Application Areas
These areas have provided classic problems in distributed/puting:
operating systems
(distributed) database systems
software fault-works
multiprocessor architectures
puting and puting
work of things (work of objects, such as household appliances)
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Course Overview: Part I (Fundamentals)
two munication models:
message passing
shared memory
two basic timing models:
synchronous
asynchronous
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Course Overview: Basic Models
Message passing Shared memory
synchronous
asynchronous
Yes
No
Yes
Yes
(Synchronous shared memory model is PRAM)
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Course