The Design and Implementation of a Log-Structured File System

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1、TheDesignandImplementationofaLog-StructuredFileSystemMendelRosenblumandJohnK.OusterhoutElectricalEngineeringandComputerSciences,ComputerScienceDivisionUniversityofCaliforniaBerkeley,CA94720mendel@sprite.berkeley.edu,ouster@sprite.berkeley.eduAbstractmagnitudemoreefficientlythancurrent

2、filesystems.ThispaperpresentsanewtechniquefordiskstorageLog-structuredfilesystemsarebasedontheassump-managementcalledalog-structuredfilesystem.Alog-tionthatfilesarecachedinmainmemoryandthatincreas-structuredfilesystemwritesallmodificationstodiskingmemorysizeswillmakethecachesmoreandmoreseq

3、uentiallyinalog-likestructure,therebyspeedingupeffectiveatsatisfyingreadrequests[1].Asaresult,diskbothfilewritingandcrashrecovery.Thelogistheonlytrafficwillbecomedominatedbywrites.Alog-structuredstructureondisk;itcontainsindexinginformationsothatfilesystemwritesallnewinformationtodiskin

4、asequen-filescanbereadbackfromthelogefficiently.Inordertotialstructurecalledthelog.Thisapproachincreaseswritemaintainlargefreeareasondiskforfastwriting,wedivideperformancedramaticallybyeliminatingalmostallseeks.thelogintosegmentsanduseasegmentcleanertoThesequentialnatureofthelogalsoper

5、mitsmuchfastercompresstheliveinformationfromheavilyfragmentedcrashrecovery:currentUnixfilesystemstypicallymustsegments.Wepresentaseriesofsimulationsthatdemon-scantheentiredisktorestoreconsistencyafteracrash,butstratetheefficiencyofasimplecleaningpolicybasedonalog-structuredfilesystemnee

6、donlyexaminethemostcostandbenefit.Wehaveimplementedaprototypelog-recentportionofthelog.structuredfilesystemcalledSpriteLFS;itoutperformsThenotionofloggingisnotnew,andanumberofcurrentUnixfilesystemsbyanorderofmagnitudeforrecentfilesystemshaveincorporatedalogasanauxiliarysmall-filewriteswhi

7、lematchingorexceedingUnixperfor-structuretospeedupwritesandcrashrecovery[2,3].How-manceforreadsandlargewrites.Evenwhentheoverheadever,theseothersystemsusethelogonlyfortemporaryforcleaningisincluded,SpriteLFScanuse70%ofthestorage;thepermanenthomeforinformationisinatradi-diskbandwidthf

8、orwriting,wh