chapter1引言ados信息學(xué)院計(jì)算機(jī)系

AdvancedOperatingDistributedSystemsConceptsandQingDepartmentofComputerScience,RenminUniversity1ChapterCharacterizationofDistributed 2DistributedSystems–ConceptsandDesign,GeorgeCouloris, Dollimore,andTimKindberg（2，3，4，5版Thelectureisbasedonthis31.1簡(jiǎn)介1.2分布式系統(tǒng)實(shí)例(Distributed1.31.4 1.61.7資源共享和web(ResourceSharingand 1.94ChallengesofDistributedWhenconstructingadistributedsystemthedesignerencouterschallengesthatarespecifictodistributedsystems.Thesizeofeachchallengedependsontherequirementsofthespecificsystem.Thosechallengescanbeassignedtoseveral （異構(gòu)性 （開(kāi)放性 （安全性 （可伸縮性 Failure （并發(fā)性 （透明性5Networks:Ethernet（以太網(wǎng)）,WLAN（無(wú)線局域網(wǎng)）,GSM（數(shù)字通）,UMTS（？軍事訓(xùn)練）,ATM,…Datatypes:integertypes,floatingpointtypes,…Computerhardware:Processor,printer,storage,…Operatingsystems:varioustypesofWindowsandUNIX,…Programminglanguages:C++,Java,Application6Commoninterfacesareneeded:TCP/IPfortheInternet,Middleware中間件Asoftwarelayerthatseparatestheapplicationfromthesystemsoftwareandhardware Itprovidesa codecanbesentfromonecomputertoanotherandrunatthedestination:Javabytecode7Inanopensystemnewservicescanbeaddedorexistingservicescanbere-implemented.Keysoftwareinterfacesofthecomponentsofanopensystemmustbestandardizedoratleastpublished.（RequestForComments征求(RFC)forInternetprotocols()，發(fā)布的。 sforCORBA(8Opendistributedsystemsarebaseduponauniformcommunicationmechanism（一致的通信機(jī)制）.OpendistributedsystemsareindependentfromindividualvendorsTheconformanceofacomponenttothepublishedstandardmustbetestedandverified.9ItismoredifficulttoachievesecurityinadistributedsystemthaninacentralizedsystemduetothevulnerabilityofComponentsof 性:Protectionagainst ）tounauthorizedindividualsorapplications防 Integrity完整性:Protectionagainstal tionorAvailability可用性Protectionagainstinterferencewiththemeanstoaccesstheresources Authentication鑒定:Reliableandcorrectidentificationofaremoteuseroranotheragent. ImportantpresentsecurityDenialofservice :Disruptionofaservicebyanotheruser.codeThiscodemayinclude 伊 心 就而言，JP一直。但在今年10月，JP了第二次，此次涉及萬(wàn)家庭和戶的、地址、、 市場(chǎng)研究機(jī)構(gòu)IDC，如今開(kāi)源軟件的觸角幾乎已名為心臟（Heartbleed）和S 。 舉例來(lái)說(shuō)，心臟 和號(hào)等隱私信息在內(nèi)的敏感其中已被確認(rèn)受影響的包括Imgur等。同時(shí)，在這一遭到披露后，有不少科技企業(yè)均表示自己會(huì)在今后 醫(yī)生如何提 ChallengeScalability（可伸縮性Asystemisscalableifitremainsefficientalthoughthereissignificantincreaseinthenumberofresourcesandthenumberofusers.ChallengestoControllingthecostofphysicalThecostforaddingnusersshouldbeatmostChallengeScalability（可伸縮性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淘寶“雙 年月日，注定會(huì)被載入互聯(lián)網(wǎng)的歷史2011年雙十一支付寶額52億元。年支付寶額億元，而今年則達(dá)到額的。 雙11當(dāng)日網(wǎng) 自 年月日，淘寶商城（現(xiàn)名天貓）拉開(kāi)網(wǎng)購(gòu)狂歡節(jié) 此時(shí) 如何設(shè) 成為眾 自 年月日，淘寶商城（現(xiàn)名天貓）拉開(kāi)網(wǎng)購(gòu)狂歡 此時(shí) 如何設(shè) 成為眾 雙11這樣的大型促銷活動(dòng)帶來(lái)的是流量暴漲，在高 瞬 此時(shí)，如何設(shè) 解決這一問(wèn)題的 做，小系統(tǒng)大做。濃縮一下就是三個(gè)字：快、穩(wěn)、炫。32Failuresinadistributedsystemarepartial–notallcomponentsfail.ThefunctioningsystemcanstillbeThehandlingoffailuresisparticularlyDetectionofacorrupteddatatransmissionbyachecksum出錯(cuò)數(shù)據(jù)傳輸?shù)脑\斷Alocalizationofafaultynetworkcomponentmaybedifficult.錯(cuò)誤網(wǎng)絡(luò)組件的定位Challenge:FailureMaskingfailures:HidingafailurefromauseroranapplicationAutomaticretransmissionofmissingUseofRAIDtostoreThosemethodsdonotworkina(rare)worstChallenge:FailureHandlingToleratingfailures容錯(cuò):The doesnotfailiftherearefailuresthatcannotbedetectedorhidden.Afterseveralunsuccessfulretransmissionattemptsthesystemgivesupandinformsthe.The continueswithotherworkandretriesthetransmissionlater.Recoveryfromfailures故障恢復(fù)Afailuredoesnotcausepermanentdamage.Afteraremoteinvocationhasbeenstoppedbyaservercrashtheoriginalstatebeforetheinvocationisrestored.Afaultycomponentisintegratedintothesystemafteritsrepair.Challenge:FailureRedundancy冗余Failurehidingcanoftenbeachievedbyuseofredundantcomponents.Differentroutesbetweentworoutersinthe Availability:TheproportionoftimeasystemisavailableforResourcesaresharedby sinadistributedAsharedresourcemaybeaccessedatthesametimebymorethanone Handlingall requestssequentiallylimitsthethroughputoftheserver.處理用戶需求序列方法限制了吞吐量。Manyservicessupportconcurrentprocessingof ConcurrentrequestsmustnotinterferewitheachServicesandobjectsmustbesafeinaconcurrent中秋來(lái)了，來(lái)了，12306也來(lái)了。一個(gè)想回級(jí)12306，新增的車票預(yù)約和排隊(duì)出票功能都17號(hào)晚上：接到?jīng)Q定回 年月日，11:0

的成功率。我覺(jué)得，我Transparencyistheconcealment（隱藏）fromtheuserandtheapplicationprogrammeroftheseparationofcomponentsinadistributedsystem.Thesystemisperceivedasasingle

Accesstransparency:LocalandremoteresourcesareaccessedbyusingidenticalmethodsFileaccessinadistributedfilesystemwithoutrequiringexplicitmethodslikeftp.Locationtransparency（位置的透明性）Resourcescanbeaccessedwithoutknowledgeoftheirlocations. Ausermaywanttoaddressaresourceataspecificlocation,likeaprinter:Locationawarecomputing.ThelocationofaresourcemustbeavailableonAccessandlocationtransparencytogetherarealsocallednetworktransparency.Challenge:TransparencyConcurrencytransparency（并發(fā)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（移動(dòng)透明性）:Resourcesand scanmoveinthesystemwithoutaffectingtheoperationofusersorprograms.Namesdonotchangewhenresourcesare Performancetransparency（性能透明性）:Thesystemcanbereconfiguredtoimproveperformancewithoutrequiringuseractivity.Theloadofthesystemisbalancedbyautomaticallymovingsomeservices.Challenge:Scalingtransparency（伸縮透明性）: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簡(jiǎn)介1.2分布式系統(tǒng)實(shí)例(Distributed1.31.4 1.61.7資源共享和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