分布式系统原理与范例_1 introductionnew

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1、IntroductionofDistributedSystemsOutline1.0Motivation1.1DefinitionofADistributedSystem1.2GoalsMakingResourcesAccessibleDistributionTransparencyOpennessScalabilityPitfalls1.3TypesofDistributedSystemsDistributedComputingSystemsDistributedInformationSystemsDistributedPervasiveSyste

2、msMotivationResourcesharing–bothphysicalresourcesandinformationComputationspeedup–tosolvelargeproblems,wewillneedmanycooperatingmachinesReliability-machinesfailfrequentlyCommunication–peoplecollaboratingfromremotesitesManyapplicationsarebytheirnaturedistributed(ATMs,airlineticketreser

3、vation,etc)TwoMainStimuliTechnologicalchangeUserneedsTechnologyadvancesNetworkingProcessorsMemoryStorageProtocolNetworkingJune1976:RobertMetcalfepresentstheconceptofEthernetattheNationalComputerConference1980:Ethernetintroducedasdefactostandard(DEC,Intel,Xerox)1985:thickEthernet

4、:10Mbps,Bus-based1991:10BaseT-twistedpair:10Mbps1995:100MbpsEthernet1998:GigabitEthernet1999:802.11bstandard2001:10Gbpsintroduced2005:100Gbps(overopticallink)NetworkConnectivityThen:largecompaniesanduniversitiesonInternetgatewaysbetweenothernetworksdial-upbulletinboards1985:1,961

5、hostsontheInternetintheworldNow:OneInternet(mostly)2011:600millionhostsontheInternetinChina,2billionintheworldwidespreadconnectivityHigh-speedWANconnectivity:1–>1GbpsSwitchedLANswirelessnetworkingcomputingpowercomputersgotsmallercheaperpowerefficientFastermicroprocessorsbecamete

6、chnologyleadersMemorymemoryhierarchiescaches•hidelatencyofmainmemoryaccess,increaseaccessbandwidthmemorygetsdenser,processorsgetfaster•largercaches–on-chipcache:1984:127bytes,today:–multilevelcaches:firstintroduced~1986,today:•cachingtechniques–reduceorhidemisslatencies–cache-awareprogr

7、ammers/compliers/computersStoragecostreducedMainMemory9,000xcheaper4,000xmorecapacityyear$/MBtypical1977$32,00016K1987$250640K-2MB1997$264MB-256MB2007$0.06512MB-2GB+Storage:disk131,000xcheaperin20years30,000xmorecapacityRecordingdensityincreasedover60,000,000