chapter1引言ados信息学院计算机系

AdvancedOperatingDistributedSystemsConceptsandQingDepartmentofComputerScience,RenminUniversity1ChapterCharacterizationofDistributed 2DistributedSystems–ConceptsandDesign,GeorgeCouloris, Dollimore,andTimKindberg（2，3，4，5版Thelectureisbasedonthis31.1简介1.2分布式系统实例(Distributed1.31.4 1.61.7资源共享和web(ResourceSharingand 1.94ChallengesofDistributedWhenconstructingadistributedsystemthedesignerencouterschallengesthatarespecifictodistributedsystems.Thesizeofeachchallengedependsontherequirementsofthespecificsystem.Thosechallengescanbeassignedtoseveral （异构性 （开放性 （安全性 （可伸缩性 Failure （并发性 （透明性5Networks:Ethernet（以太网）,WLAN（无线局域网）,GSM（数字通）,UMTS（？军事训练）,ATM,…Datatypes:integertypes,floatingpointtypes,…Computerhardware:Processor,printer,storage,…Operatingsystems:varioustypesofWindowsandUNIX,…Programminglanguages:C++,Java,Application6Commoninterfacesareneeded:TCP/IPfortheInternet,Middleware中间件Asoftwarelayerthatseparatestheapplicationfromthesystemsoftwareandhardware Itprovidesa codecanbesentfromonecomputertoanotherandrunatthedestination:Javabytecode7Inanopensystemnewservicescanbeaddedorexistingservicescanbere-implemented.Keysoftwareinterfacesofthecomponentsofanopensystemmustbestandardizedoratleastpublished.（RequestForComments征求(RFC)forInternetprotocols()，发布的。 sforCORBA(8Opendistributedsystemsarebaseduponauniformcommunicationmechanism（一致的通信机制）.OpendistributedsystemsareindependentfromindividualvendorsTheconformanceofacomponenttothepublishedstandardmustbetestedandverified.9ItismoredifficulttoachievesecurityinadistributedsystemthaninacentralizedsystemduetothevulnerabilityofComponentsof 性:Protectionagainst ）tounauthorizedindividualsorapplications防 Integrity完整性:Protectionagainstal tionorAvailability可用性Protectionagainstinterferencewiththemeanstoaccesstheresources Authentication鉴定:Reliableandcorrectidentificationofaremoteuseroranotheragent. ImportantpresentsecurityDenialofservice :Disruptionofaservicebyanotheruser.codeThiscodemayinclude 伊 心 就而言，JP一直。但在今年10月，JP了第二次，此次涉及万家庭和户的、地址、、 市场研究机构IDC，如今开源软件的触角几乎已名为心脏（Heartbleed）和S 。 举例来说，心脏 和号等隐私信息在内的敏感其中已被确认受影响的包括Imgur等。同时，在这一遭到披露后，有不少科技企业均表示自己会在今后 医生如何提 ChallengeScalability（可伸缩性Asystemisscalableifitremainsefficientalthoughthereissignificantincreaseinthenumberofresourcesandthenumberofusers.ChallengestoControllingthecostofphysicalThecostforaddingnusersshouldbeatmostChallengeScalability（可伸缩性ControllingtheperformancelossThecomputationalcomplexityofmethodstomanagenusersshouldbeO(logn).PreventingsoftwareresourcesfromrunningIPV4limitsthenumberofaddressestoConversiontoIPV6isrequiredtomaintainAlgorithmsinascalablesystemsshouldbeComputersinthe 1979,01989,01999,2003,Figure (第四版)FigureGrowthoftheInternet(computersandwebWeb1993,1995,1997,61999,2001,2003,2005,Instructor’sGuideforCoulouris,Dollimore,KindbergandBlair,DistributedSystems:ConceptsandDesignEdn.©PearsonEducation淘宝“双 年月日，注定会被载入互联网的历史2011年双十一支付宝额52亿元。年支付宝额亿元，而今年则达到额的。 双11当日网 自 年月日，淘宝商城（现名天猫）拉开网购狂欢节 此时 如何设 成为众 自 年月日，淘宝商城（现名天猫）拉开网购狂欢 此时 如何设 成为众 双11这样的大型促销活动带来的是流量暴涨，在高 瞬 此时，如何设 解决这一问题的 做，小系统大做。浓缩一下就是三个字：快、稳、炫。32Failuresinadistributedsystemarepartial–notallcomponentsfail.ThefunctioningsystemcanstillbeThehandlingoffailuresisparticularlyDetectionofacorrupteddatatransmissionbyachecksum出错数据传输的诊断Alocalizationofafaultynetworkcomponentmaybedifficult.错误网络组件的定位Challenge:FailureMaskingfailures:HidingafailurefromauseroranapplicationAutomaticretransmissionofmissingUseofRAIDtostoreThosemethodsdonotworkina(rare)worstChallenge:FailureHandlingToleratingfailures容错:The doesnotfailiftherearefailuresthatcannotbedetectedorhidden.Afterseveralunsuccessfulretransmissionattemptsthesystemgivesupandinformsthe.The continueswithotherworkandretriesthetransmissionlater.Recoveryfromfailures故障恢复Afailuredoesnotcausepermanentdamage.Afteraremoteinvocationhasbeenstoppedbyaservercrashtheoriginalstatebeforetheinvocationisrestored.Afaultycomponentisintegratedintothesystemafteritsrepair.Challenge:FailureRedundancy冗余Failurehidingcanoftenbeachievedbyuseofredundantcomponents.Differentroutesbetweentworoutersinthe Availability:TheproportionoftimeasystemisavailableforResourcesaresharedby sinadistributedAsharedresourcemaybeaccessedatthesametimebymorethanone Handlingall requestssequentiallylimitsthethroughputoftheserver.处理用户需求序列方法限制了吞吐量。Manyservicessupportconcurrentprocessingof ConcurrentrequestsmustnotinterferewitheachServicesandobjectsmustbesafeinaconcurrent中秋来了，来了，12306也来了。一个想回级12306，新增的车票预约和排队出票功能都17号晚上：接到决定回 年月日，11:0

的成功率。我觉得，我Transparencyistheconcealment（隐藏）fromtheuserandtheapplicationprogrammeroftheseparationofcomponentsinadistributedsystem.Thesystemisperceivedasasingle

Accesstransparency:LocalandremoteresourcesareaccessedbyusingidenticalmethodsFileaccessinadistributedfilesystemwithoutrequiringexplicitmethodslikeftp.Locationtransparency（位置的透明性）Resourcescanbeaccessedwithoutknowledgeoftheirlocations. Ausermaywanttoaddressaresourceataspecificlocation,likeaprinter:Locationawarecomputing.ThelocationofaresourcemustbeavailableonAccessandlocationtransparencytogetherarealsocallednetworktransparency.Challenge:TransparencyConcurrencytransparency（并发透明性）:Severalprocessescanoperateconcurrentlyonsharedresourceswithoutinterferenceamongthem。seetheconcurrencyThesystemneedstopreventundesired（不希望的）concurrentactivities.TwouserscannotmodifythesamefileUseoflocksorChallenge:Replicationtransparency（ 透明性）:MultipleinstancesofresourcescanbeusedtoincreasereliabilityandperformancewithoutknowledgeofthereplicasbyusersorapplicationReplicasoffileserversinsomedistributedfileFailuretransparency（故障透明性）Faultsspecifictodistributedsystemsareconcealedfromusersandapplicationprograms分seethefailurehandlingChallenge:TransparencyMobility(migration)transparency（移动透明性）:Resourcesand scanmoveinthesystemwithoutaffectingtheoperationofusersorprograms.Namesdonotchangewhenresourcesare Performancetransparency（性能透明性）:Thesystemcanbereconfiguredtoimproveperformancewithoutrequiringuseractivity.Theloadofthesystemisbalancedbyautomaticallymovingsomeservices.Challenge:Scalingtransparency（伸缩透明性）:Thesystemandthescaleofitsapplicationscangrowwithoutrequiringachangeinthesystemstructureortheapplicationalgorithms,seethescalabilitychallenge.

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Section1.5.7Accesstransparency:enableslocalandremoteresourcestobeaccessedusingidenticalLocationtransparency:enablesresourcestobeaccessedwithoutknowledgeoftheirphysicalornetworklocation(forexample,whichbuildingorIPaddress).Concurrencytransparency:enablesseveralprocessestooperateconcurrentlyusingsharedresourceswithoutinterferencebetweenthem.Replicationtransparency:enablesmultipleinstancesofresourcestobeusedtoincreasereliabilityandperformancewithoutknowledgeofthereplicasbyusersorapplicationprogrammers.Failuretransparency:enablestheconcealmentoffaults,allowingusersandapplicationprogramstocompletetheirtasksdespitethefailureofhardwareorsoftwareMobilitytransparency:allowsthemovementofresourcesandwithoutaffectingtheoperationofusersorprograms.

swithinaPerformancetransparency:allowsthesystemtobereconfiguredtoimprove asloadsvary.Scalingtransparency:allowsthesystemandapplicationstoexpandinscalewithout tothesystemstructureortheapplicationalgorithms.Instructor’sGuideforCoulouris,Dollimore,KindbergandBlair,DistributedSystems:ConceptsandDesignEdn.©PearsonEducation1.1简介1.2分布式系统实例(Distributed1.31.4 1.61.7资源共享和web(ResourceSharingand 1.9WhohasusedWhowasprogrammedinWhohasprogrammedunderDoyouhavedepartmentalPeopleLoveWebServers:LinuxvsWindowsWhypeoplelikepowerfulandhardto andGettingStartedWithUNIXSectionA:ObjectivesAfterstudyingthislesson,youshouldbeableDefineoperatingsystemsinDescribeLinuxasitrelatesto inthefunctionofUNIX DescribetheoptionsforconnectingtoaUNIXGettingStartedWithUNIXSectionA:ObjectivesAfterstudyingthislesson,youshouldbeableUsethedate,who,man,etc.EntermultiplecommandsonasinglecommandRecallacommandfromthecommandLogontoandlogoutofUnderstandingOperatingAnoperatingsystem(OS)isthemostimportantprogramthatrunsonacomputerOperatingsystemsenableyoutostoreinformation,processrawdata,useapplicationsoftware,compileyourownprograms,andaccessallhardwareattachedtoacomputerOperatingSystemWherecanwefindGameGameNetworkCommonPCOperatingA alcomputer(PC)OSconductsallI/O,processing,andstorageoperationsonastand-alonecomputer.CommonMainframeOperatingAmainframeOScontrolsalargecomputersystemwithmultipleprocessorsforI/O,processing,andstorageoperationsformanyusersRelationshipofServers sonaAnetworkOScontrolstheoperationsofaservercomputer(host),whichacceptsrequestsfromuserprogramsrunningonothercomputers( IntroducingtheUNIXOperatingUNIXisamulti-user,multitaskingoperatingsystemwithbuilt-innetworkinghistoric,butrare(onlyafewPDAsuseSingle-user,multi-SomePCsandworkstationsmaybeconfiguredlikethis.e.g.,Windowsusedonlarge,mainframesandPCs,workstationsandserverstoday.e.g.UNIX,WindowsXP,LinuxIntroducingtheUNIXOperatingUNIXisamulti-usersystem,whichletsmanypeoplesimultaneouslyaccessandsharetheresourcesofaservercomputerAmultitaskingsystemletsoneuserexecutemorethanoneprogramatatimeUNIXisalsoaportableoperatingIntroducingtheUNIXOperatingItsportabilitymeansitcanbeusedinavarietyofcomputingTraditionally,mostoperatingsystemswerewritteninAssembler,foraspecificVERYpainful-ifatallpossible-to`port'theoperatingsystemtootherUNIXismostlywrittenintheClanguage.ThisaloneallowsUNIXtobeportabletomanyarchitectures.UNIXrunsonawidervarietyofcomputersthananyotheroperatingABriefHistoryofAgroupofprogrammersatBellLabsoriginallydevelopedUNIXintheearlyBellLabsdistributedUNIXinitssourcecodeform,soanyonewhousedUNIXcouldcustomizeitasneededEventually,twostandardversionofUNIXAT&TproducedSystemVUniversityofCaliforniaatBerkeleydevelopedBSD(BerkeleySystemDistribution,2BSD,1978)ABriefHistoryofLayersofaUNIX s,ls,cp,Netscape,vi,pine,UNIX DOSand WindowsadoptedoriginalUNIXdesignconcepts,suchastheideaofas --aninterfacebetweentheuserandtheoperatingsystem--andthehierarchicalstructureofdirectoriesandThekernelisthebaseoperatingsystem,whichin ctsdirectlywiththe