lecture_15_file_system Implementation

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1、File-systemImplementationZhaoFangOperatingSystems-forthecollagestudentsGoalforTodayFile-SystemStructureFile-SystemImplementationDirectoryImplementationFree-SpaceManagementUnixFileManagementLinuxVirtualFileSystemWindowsFileSystemObjectivesTodescri

2、bethedetailsofimplementinglocalfilesystemsanddirectorystructuresTodescribetheimplementationofremotefilesystemsTodiscussblockallocationandfree-blockalgorithmsandtrade-offsFile-SystemStructureFilestructureLogicalstorageunitCollectionofrelatedinformati

3、onFilesystemresidesonsecondarystorage(disks)Provideduserinterfacetostorage,mappinglogicaltophysicalProvidesefficientandconvenientaccesstodiskbyallowingdatatobestored,locatedretrievedeasilyFile-SystemStructureDiskprovidesin-placerewriteandrandomaccess

4、I/Otransfersperformedinblocksofsectors(usually512bytes)Filecontrolblock–storagestructureconsistingofinformationaboutafileDevicedrivercontrolsthephysicaldeviceFilesystemorganizedintolayersTypicalsoftwareorganizationDeviceDriversLowestlevelCommunicat

5、esdirectlywithperipheraldevicesResponsibleforstartingI/OoperationsonadeviceProcessesthecompletionofanI/OrequestBasicFileSystemPhysicalI/OPrimaryinterfacewiththeenvironmentoutsidethecomputersystemDealswithexchangingblocksofdataConcernedwiththeplacem

6、entofblocksConcernedwithbufferingblocksinmainmemoryBasicI/OSupervisorResponsibleforallfileI/Oinitiationandtermination.Controlstructuresdealwith•DeviceI/O,•Scheduling,•Filestatus.•SelectsandschedulesI/OwiththedeviceLogicalI/OEnablesusersandapplication

7、stoaccessrecordsProvidesgeneral-purposerecordI/OcapabilityMaintainsbasicdataaboutfileElementsofFileManagementFile-SystemImplementationBootcontrolblockcontainsinfoneededbysystemtobootOSfromthatvolumeNeededifvolumecontainsOS,usuallyfirstblockofvolumeV

8、olumecontrolblock(superblock,masterfiletable)containsvolumedetailsTotal#ofblocks,#offreeblocks,blocksize,freeblockpointersorarrayDirectorystructureorganizesthefilesNamesandinodenumbers,masterfiletableFile-SystemImplemen