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1、Chapter1ACaseforRedundantArraysofInexpensiveDisks(RAID)DAVIDA.PATTERSON,GARTHGIBSON,“Joy'sLaw”,copebyofferingmultiprocessorsastheirtop-ANDRANDYH.KATZof-the-lineproduct.ButafastCPUdoesnotafastsystemmake.GeneComputerScienceDivisionAmdahlrelatedCPUspeedtomainmemorysizeusingDepartment
2、ofElectricalEngineeringandComputerSciencesthisrule[Siewiorek82]571EvansHallUniversityofCaliforniaEachCPUinstructionpersecondrequiresonebyteofBerkeley,CA94720mainmemory.AbstractIfcomputersystemcostsarenottobedominatedbythecostofmemory,thenAmdahl'sconstantsuggeststhatmemorychipcapac
3、ityshouldgrowatthesamerate.IncreasingperformanceofCPUsandmemorieswillbeGordonMoorepredictedthatgrowthrateover20yearssquanderedifnotmatchedbyasimilarperformanceagoincreaseinI/O.WhilethecapacityofSingleLargeExpensiveDisk(SLED)hasgrownrapidly,thetransistors/chip=2Year-1964performance
4、improvementofSLEDhasbeenmodest.AspredictedbyMoore’sLaw,RAMshavequadrupledinRedundantArraysofInexpensiveDisks(RAID),basedoncapacityeverytwo[Moore75]tothreeyears[Moore86].themagneticdisktechnologydevelopedforpersonalRecentlythisratioofmegabytesofmainmemorytocomputers,offersanattract
5、ivealternativetoSLED,MIPShasbeendefinedasalpha[Garcia84],withpromisingimprovementsofanorderofmagnitudeinAmdahl'sconstantmeaningalpha=1.Inpartbecauseofperformance,reliability,powerconsumption,andtherapiddropofmemoryprices,mainmemorysizeshavescalability.Thispaperintroducesfivelevels
6、ofRAIDs,grownfasterthanCPUspeedsandmanymachinesaregivingtheirrelativecost/performance,andcomparesshippedtodaywithalphasof3orhigher.RAIDstoanIBM3380andaFujitsuSuperEagle.Tomaintainthebalanceofcostsincomputersystems,secondarystoragemustmatchtheadvancesinotherpartsofthesystem.Akeymea
7、sureofdisktechnologyisthe1.1Background:RisingCPUandgrowthinthemaximumnumberofbitsthatcanbestoredMemoryPerformancepersquareinch,orthebitsperinchinatracktimesthenumberoftracksperinchCalledMAD,formaximalTheusersofcomputersarecurrentlyenjoyingarealdensity,the“FirstLawinDiskDensity”pre
8、dictsunprecedentedgrowthinthespee
