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ComputerComputerOrganization&DesignOrganization&Design——TheHardware/SoftwareInterfaceTheHardware/SoftwareInterface25/1/271ContentsofChapter6ContentsofChapter66.1Introduction6.2Dependability,Reliability,andAvailability6.3DiskStorage6.4FlashStorage6.5ConnectingProcessors,Memory,andI/ODevices6.6InterfacingI/ODevicestotheProcessor,Memory,andOperatingSystem6.7I/OPerformanceMeasures:ExamplesfromDiskandFileSystems6.8DesigninganI/OSystem6.9ParallelismandI/O:RedundantArraysofInexpensiveDisks225/1/27I/ODesignersmustconsidermanyfactorssuchasexpandabilityandresilience(resume),aswellasperformance.AssessingI/Osystemperformanceisverydifficult.Indifferentsituations,needsusedifferentmeasurements.PerformanceofI/Osystemdependson:connectionbetweendevicesandthesystemthememoryhierarchytheoperatingsystem36.1Introduction6.1Introduction25/1/27AtypicalcollectionofI/OdevicesAtypicalcollectionofI/OdevicesMainmemoryI/OcontrollerI/OcontrollerI/OcontrollerDiskGraphicsoutputNetworkMemory-I/ObusProcessorCacheInterruptsDisk425/1/27ThreecharacteristicsBehaviorInput(readonce),output(writeonly,cannotread),orstorage(canberereadandusuallyrewritten)PartnerEitherahumanoramachineisattheotherendoftheI/Odevice,eitherfeedingdataoninputorreadingdataonoutput.DatarateThepeakrateatwhichdatacanbetransferredbetweentheI/Odeviceandthemainmemoryorprocessor.525/1/27I/Operformancedependsontheapplication:throughput:Inthesescases,I/Obandwidthwillbemostimportant.EvenI/Obandwidthcanbemeasuredintwodifferentwaysaccordingtodifferentsituations:1.Howmuchdatacanwemovethroughthesysteminacertaintime?Forexamples,inmanysupercomputerapplications,mostI/Orequiresareforlongstreamsofdata,andtransferbandwidthistheimportantcharacteristic.I/Orequests:ReadsorwrilestoI/0devices.625/1/272.HowmanyI/Ooperationscanwedoperunitoftime?Forexample,NationalIncomeTaxServicemainlyprocesseslargenumberofsmallfiles.responsetime(e.g.,workstationandPC)boththroughputandresponsetime(e.g.,ATM)725/1/27T...