maximumwindowsnt

WindowsOSFileSystemsMS-DOSandWindows95/98/NT/2000/XPallowuseofFAT-16orFAT-32.
WindowsNT/2000/XPusesNTFS(NTFileSystem)FileAllocationTable(FAT)Notusedsomuch,butlookatasacontrasttootherlesystems.
DiskLayoutSeeoldTanenbaumFig8-18.
Bootsector|Partition1|Partion2|.
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Eachpartitioncanbeadierentlesystem(includingUnix).
Eachpartitionislaidoutas:SecondaryBootSector|FAT|OptionalDuplicateFAT|Rootdirectory|Datablocks.
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CS45131week2-windowsfs.
texFileAllocationTable(FAT)Haveatablewithoneentryforeachblockonthedisk.
Directoryentryforalecontainstherstblockinthele.
TheFATentryforthisblockthenpointstothenextblockofthele.
UseEOFmarkforlastblock.
Blankentriesindicatefreeblocks(noneedforfreeblocklist).
Example(alsoseeoldTanenbaumFig8-19):BlockEntry0Bootsector1Bootsector23374Free5EOF610758Free9Bad10EOFThebootsectorcontainsbootinstructionsanddescriptiveinfolike:sizeofdisksector,numberofphysicalsectorsondiskperblock,sizeofrootdirectory.
Badentryindicatesblockisnotusable.
With16-bitblockshaveamaximumof216=64Kblocks.
Tousea2GBdiskonewouldneed32K-byteblocks(verylarge).
Canresultininternalfragmentationforsmallles.
FAT-32uses32-bitblocknumberssupporting4GBofblocknumbersanddisksupto2Terabytesinsize.
CS45132week2-windowsfs.
texFAT-16DirectoryEntryEachdirectoryentryis32bytes:FileName(8bytes)Extension(3bytes)Attributes(1byte)Reserved(10bytes)Time(2bytes)Date(2bytes)Blocknumberofrstleblock(2bytes)Filesizeinbytes(4bytes)Attributes(one-biteach):R:ReadOnlyA:Archive(setwhenlemodied,clearedwhenbackedup)S:SystemFile(lecannotbedeletedbythedelcommand)H:HiddenFile(leisnotlistedwithdircommand)D:DirectoryV:VolumeLabelNote:FATanddirectoryentrybothkeeptrackofhowmanyblocksinale—couldbeinconsistency.
FAT(versusUnix)keepsallinformationaboutaleinthedirectoryentryratherthananinode.
CS45133week2-windowsfs.
texFAT-32FileSystemBlocknumbersare32-bitslong.
FATitselfbecomeslargerandtwoofthereservedbytesindirectoryentryareusedtoextendblocknumberto4bytes.
FAT-32alsoabolishedtherestrictiononthesizeoftherootdirectory—therootdirectoryisnolongerstoredinaxedposition.
LikeFAT-16,hasnoaccessprotectionforles.
LongFileNamesVFAT(virtualleallocationtable)isusedinWindows95/98tohandlelonglenames.
UseareservedareaofVFATforlonglenameswithaninvalidcombinationofattributebitsindirectoryentries.
CS45134week2-windowsfs.
texNT/2000/XPFileSystem(NTFS)FileSystemAPICallsLookatTanenbaumFigures11-31and11-33—similartoUnix/Linux.
OrganizationFundamentalentityinNTFSisavolume.
LikeapartitioninFAT,butoccupypart,allormultipledisks.
Usesclusters(basicallysameasablock)astheunitofdiskallocation.
Aclusterconsistsofoneormorephysicalsectorsonthedisk.
Theyarenumberedbynumberscalledlogicalclusternumbers(LCNs).
InformationaboutNTFSlesstoredasattributes:lename(namesiftherearealiases),creationtime,securitydescriptor,unnameddataattribute(contentsofthele).
MasterFileTable(MFT)Speciallecontainingoneentryforeachleinavolume.
MFTentrycanbefrom1KBto4KB.
InfocontainedinanMFTentryaboutale:standardinfosuchastimestamps,lesizele'snameinUnicode(16-bitchars)andalsoan8.
3DOS-stylenamesecurityinfodataforthele.
IfasmalllethisattributecanbestoredintheMFTentry(residentattributevs.
non-residentattribute).
MoredetailsifleislargerinkeepingtrackofwhichLCNsareused.
SeeFig11-35forallattributesthatcanappearinMFTrecords.
Attributesareaccessedusingle-name:attributesyntax.
CS45135week2-windowsfs.
texDirectoryThecontentsofadirectoryarestoredasaleandcontainanindextothelesinthisdirectory.
TheindexisstoredasaB+treeforfastlookupoflenames.
Eachleentrystoresthelename,thenumberofitsMFTentry,itstimestampandlesize.
LattertwovaluesareduplicatedfromleMFTentryforfasterdirectorylistings.
NTFSVolumeMetadataNTFSvolumemetadataisstoredinles:MFTitselfcopyoftheMFTLoglerecordsallmetadatatransactionstoallowrecoveryfromcrashesattribute-denitiontableindicatingwhichattributetypesareusedinthevolumeandwhatoperationscanbeperformedonthem.
RootdirectoryBitmaptoshowwhichclustersareallocatedBootle(tobootthesystem)Badclusterle(clusterstoavoid)(TanenbaumFig.
11-34)OtherNTFSsupportstransparentlecompression.
Supportsleencryptionwithpublic-keyencryptionSupportsdierentRAIDlevels.
CS45136week2-windowsfs.
tex