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1、TheDesignandImplementationofaLog-StructuredFileSystemMendelRosenblumandJohnK.OusterhoutElectricalEngineeringandComputerSciences,ComputerScienceDivisionUniversityofCaliforniaBerkeley,CA94720mendel@sprite.berkeley.edu,ouster@sprite.berkeley.eduAbstractmagnitudemoreef?cientlythancurrent
2、?lesystems.ThispaperpresentsanewtechniquefordiskstorageLog-structured?lesystemsarebasedontheassump-managementcalledalog-structured?lesystem.Alog-tionthat?lesarecachedinmainmemoryandthatincreas-structured?lesystemwritesallmodi?cationstodiskingmemorysizeswillmakethecachesmoreandmoreseq
3、uentiallyinalog-likestructure,therebyspeedingupeffectiveatsatisfyingreadrequests[1].Asaresult,diskboth?lewritingandcrashrecovery.Thelogistheonlytraf?cwillbecomedominatedbywrites.Alog-structuredstructureondisk;itcontainsindexinginformationsothat?lesystemwritesallnewinformationtodiskin
4、asequen-?lescanbereadbackfromthelogef?ciently.Inordertotialstructurecalledthelog.Thisapproachincreaseswritemaintainlargefreeareasondiskforfastwriting,wedivideperformancedramaticallybyeliminatingalmostallseeks.thelogintosegmentsanduseasegmentcleanertoThesequentialnatureofthelogalsoper
5、mitsmuchfastercompresstheliveinformationfromheavilyfragmentedcrashrecovery:currentUnix?lesystemstypicallymustsegments.Wepresentaseriesofsimulationsthatdemon-scantheentiredisktorestoreconsistencyafteracrash,butstratetheef?ciencyofasimplecleaningpolicybasedonalog-structured?lesystemnee
6、donlyexaminethemostcostandbene?t.Wehaveimplementedaprototypelog-recentportionofthelog.structured?lesystemcalledSpriteLFS;itoutperformsThenotionofloggingisnotnew,andanumberofcurrentUnix?lesystemsbyanorderofmagnitudeforrecent?lesystemshaveincorporatedalogasanauxiliarysmall-?lewriteswhi
7、lematchingorexceedingUnixperfor-structuretospeedupwritesandcrashrecovery[2,3].How-manceforreadsandlargewrites.Evenwhentheoverheadever,theseothersystemsusethelogonlyfortemporaryforcleaningisincluded,SpriteLFScanuse70%ofthestorage;thepermanenthomeforinformationisinatradi-diskbandwidthf
8、orwriting,wh
