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1、AnImplementationofaLog-StructuredFileSystemforUNIXMargoSeltzer±HarvardUniversityKeithBostic±UniversityofCalifornia,BerkeleyMarshallKirkMcKusick±UniversityofCalifornia,BerkeleyCarlStaelin±Hewlett-PackardLaboratoriesABSTRACTResearchresults[ROSE91]demonstratethatalog-structured?lesystem(LF
2、S)offersthepotentialfordramaticallyimprovedwriteperformance,fasterrecoverytime,andfaster?lecreationanddeletionthantraditionalUNIX?lesystems.ThispaperpresentsaredesignandimplementationoftheSprite[ROSE91]log-structured?lesystemthatismorerobustandintegratedintothevnodeinterface[KLEI86].Mea
3、surementsshowitsperformancetobesuperiortothe4BSDFastFileSystem(FFS)inavarietyofbenchmarksandnotsigni?cantlylessthanFFSinanytest.Unfortunately,anenhancedversionofFFS(withreadandwriteclustering)[MCVO91]providescomparableandsometimessuperiorperformancetoourLFS.However,LFScanbeextendedtopro
4、videadditionalfunctionalitysuchasembeddedtransactionsandversioning,noteasilyimplementedintraditional?lesystems.1.IntroductionThelog-structured?lesystem,asproposedin[OUST88],attemptstoaddressbothoftheseprob-EarlyUNIX?lesystemsusedasmall,?xedlems.ThefundamentalideaofLFSistoimproveblocksiz
5、eandmadenoattempttooptimizeblock?lesystemperformancebystoringall?lesystemplacement[THOM78].Theyassigneddiskdatainasingle,continuouslog.Sucha?lesystemaddressestonewblocksastheywerecreated(preal-isoptimizedforwriting,becausenoseekisrequiredlocation)andwrotemodi?edblocksbacktotheirbetweenw
6、rites.Itisalsooptimizedforreading?lesoriginaldiskaddresses(overwrite).Inthese?lesys-writtenintheirentiretyoverabriefperiodoftimetems,thediskbecamefragmentedovertimesothat(asisthenorminUNIXsystems),becausethe?lesnew?lestendedtobeallocatedrandomlyacrosstheareplacedcontiguouslyondisk.Final
7、ly,itprovidesdisk,requiringadiskseekper?lesystemreadortemporallocality,inthatitisoptimizedforaccess-writeevenwhenthe?lewasbeingreadsequentially.ing?lesthatwerecreatedormodi?edatapproxi-TheFastFileSystem(FFS)[MCKU84]matelythesametime.dramaticallyincreased?lesystemperformance.ItT
