lecture_14_file_system Interface

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1、File-systemInterfaceZhaoFangOperatingSystems-forthecollagestudentsGoalforTodayFileConceptAccessMethodsFileDirectoriesFile-SystemMountingFileSharingProtectionObjectiveforthischapterToexplainthefunctionoffilesystems.Todescribetheinterfacestofilesystems.Todiscussfi

2、le-systemdesigntradeoffs,includingaccessmethods,filesharing,filelocking,anddirectorystructures.Toexplorefile-systemprotection.FilesFilesarethecentralelementtomostapplicationsTheFileSystemisoneofthemostimportantpartoftheOStoauserDesirablepropertiesoffiles:Long-termex

3、istenceSharablebetweenprocessesStructureFileConceptContiguouslogicaladdressspaceTypes:DatanumericcharacterbinaryProgramContentsdefinedbyfile’screatorManytypesConsidertextfile,sourcefile,executablefileFieldsandRecordsFieldsBasicelementofdataContainsasinglev

4、alueCharacterizedbyitslengthanddatatypeRecordsCollectionofrelatedfieldsTreatedasaunitFileandDatabaseFileHavefilenamesIsacollectionofsimilarrecordsTreatedasasingleentityMayimplementaccesscontrolmechanismsDatabaseCollectionofrelateddataRelationshipsexistamongel

5、ementsConsistsofoneormorefilesFileManagementSystemsProvidesservicestousersandapplicationsintheuseoffilesThewayauserorapplicationaccessesfilesProgrammerdoesnotneedtodevelopfilemanagementsoftwareObjectivesforaFileManagementSystemMeetthedatamanagementneedsoftheuserGua

6、ranteethatthedatainthefilearevalidOptimizeperformanceProvideI/OsupportforavarietyofstoragedevicetypesMinimizelostordestroyeddataProvideastandardizedsetofI/OinterfaceroutinestouserprocessesProvideI/Osupportformultipleusers(ifneeded)Requirementsforageneralpurposesyste

7、m1.Eachusershouldbeabletocreate,delete,read,writeandmodifyfiles2.Eachusermayhavecontrolledaccesstootherusers’files3.Eachusermaycontrolwhattypeofaccessesareallowedtotheusers’files4.Eachusershouldbeabletorestructuretheuser’sfilesinaformappropriatetotheproblemRequirementsco

8、nt.5.Eachusershouldbeabletomovedatabetweenfiles6.Eachusershouldbeabletobackupandrecovertheuser’sfilesin