The Design and Implementation of a Log-Structured File System文稿

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

2、ntfilesystems.ThispaperpresentsanewtechniquefordiskstorageLog-structuredfilesystemsarebasedontheassump-managementcalledalog-structuredfilesystem.Alog-tionthatfilesarecachedinmainmemoryandthatincreas-structuredfilesystemwritesallmodificationstodiskingmemorysizeswillmakethecachesmoreandmor

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

4、diskinasequen-filescanbereadbackfromthelogefficiently.Inordertotialstructurecalledthelog.Thisapproachincreaseswritemaintainlargefreeareasondiskforfastwriting,wedivideperformancedramaticallybyeliminatingalmostallseeks.thelogintosegmentsanduseasegmentcleanertoThesequentialnatureofthelo

5、galsopermitsmuchfastercompresstheliveinformationfromheavilyfragmentedcrashrecovery:currentUnixfilesystemstypicallymustsegments.Wepresentaseriesofsimulationsthatdemon-scantheentiredisktorestoreconsistencyafteracrash,butstratetheefficiencyofasimplecleaningpolicybasedonalog-structuredfil

6、esystemneedonlyexaminethemostcostandbenefit.Wehaveimplementedaprototypelog-recentportionofthelog.structuredfilesystemcalledSpriteLFS;itoutperformsThenotionofloggingisnotnew,andanumberofcurrentUnixfilesystemsbyanorderofmagnitudeforrecentfilesystemshaveincorporatedalogasanauxiliarysmall-

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

8、diskbandwidthforwriting,wh