硬盘技术磁道扇区柱面和磁头数

硬盘技术：磁道,扇区,柱面和磁头数硬盘技术:磁道,扇区,柱面和磁头数Harddisktechnology:tracks,sectors,cylinders,andheads..txtdidyourmomthrowthemupwhenyouwerebornandkeeptheplacentabig?Don'ttreatshrimpsasseafood.Don'ttreatshrimpsasseafood.1.tracks,sectors,cylinders,andheadsThebasiccomponentofaharddiskisadiskmadeofhardmetalmaterialcoatedwithmagneticmedium,varyinginnumberofdisksofdifferentcapacities.Eachdiskhastwosidesthatrecordinformation.Thediskisdividedintomanyfan-shapedregions,eachofwhichiscalledasector.Eachsectorcanstore128*2Ntimes(N=0.1.2.3)byteinformation.InDOS,eachsectoris128*2ofthe2square=512bytes,thedisksurfacewiththecenterofthediskasthecenter,concentricringsofdifferentradiiarecalledtracks.Acylinderconsistingoftracksofthesameradiusanddifferentdisksinaharddiskiscalledacylinder.Trackandcylinderaredifferentradiusofthecircle,onmanyoccasions,trackandcylindercanbeusedinterchangeably,weknowthateachdiskhastwofaces,eachfacehasahead,headnumberusedtodistinguish.Sectors,tracks(orcylinders)andnumberofmagneticheadsformthebasicparametersoftheharddiskstructure,andthecapacityoftheharddiskcanbeobtainedbyusingtheseparameters:Storagecapacity=headnumber*track(cylinder)number*persectornumber*persectorbyteMainpoints:(1)theharddiskhasseveraldisks,eachofwhichhastwoplanes,eachwithamagnetichead(2)thediskisdividedintoseveralsectors,namelysector(3)concentriccircleswithdifferentradiionthesamediskaretracks(4)cylindricalsurfacewithdifferentradii,namelycylinder;(5)formula:storagecapacity=magneticheadnumber*track(cylinder)number*persectornumber*persectorbytenumber(6)theinformationrecordscanberepresentedas**tracks(cylinders),*heads,**sectorsThe2.clusterAclusteristhesmallestunitinwhichDOSisassigned.Whenasmallfileiscreated,suchasabyte,itdoesnottakeuponlyonebyteofspaceondisk,butoccupiestheentirecluster.DOSdependingonthestoragemedium(suchasfloppydisk,harddisk),differentcapacityoftheharddisk,thesizeoftheclusterisnotthesame.Thesizeoftheclustercanbeobtainedinthediskparameterblock(BPB).Theconceptofclustersappliesonlytodataregions.Thispoint:(1)theclusteristhesmallestunitforDOSallocation.(2)differentstoragemedia,differentcapacityharddisk,differentDOSversion,thesizeofclusterisnotthesame.(3)theconceptofclustersappliesonlytodataregions.3.sectornumberdefinition:absolutesectorandDOSsectorIntroduceaccordingtothefront,wecanusethecylinder/head/sectortoeveryareaoftheuniquelocationonthedisk,orthateverycylinder/head/disksectorsectorandcorrespondingrelation,usuallyDOScylinder/head/sector"sucharepresentationcalled"absolutesector"representation.ButDOScannotuseabsolutesectortomanagetheinformationondiskinsteadofusingtheso-called"relativesector"or"DOSsector"".Therelativesectorisjustanumber,suchascylinder140,head3,andsector4correspondingtothesectornumber2757.Thenumberisinone-to-onecorrespondencewiththeabsolutesector"cylinder/head/sector".Whenusingtherelativesectornumber,DOSisfromthecylinder0,head1,sector1starts(Note:cylinder0,head0,sector1noDOSsectornumber,DOScannotaccess,BIOScanbecalledthefirstvisit),DOSsectornumberis0,theremainingsectornumberis1tothetrack16(17persector),thentheheadnumberis2,17forcylindricalsector0,theformationoftheDOSsector,from17to33.Allheadsofthecylinder.Thenmovetocylinder1,head1,sector1tocontinuethenumberingoftheDOSsector,thatis,accordingtothefanareacode,headnumber,cylindernumber(tracknumber)intheorderofgrowth,thecontinuousdistributionofDOSfanareacode.Formula:rememberthefirstheadnumberDHDOSsectorCylindernumberDCfirstDOSsectorThefirstDSDOSsectorsectorNSsectorspertrackThetotalnumberofNHdiskheadTherelativesectornumberofasector(cylinderC,headH,sectorS)isRS:RS=NH*NS*(CDC)NS*(HDH)+(SDS)IfRS,DC,DH,DS,NS,andNHareknown,thenS=(RSMODNS)DS(H=(RSDIVNS)MODNH)DH(C=(RSDIVNS)DIVNH)DCMainpoints:(1)theabsolutesectorrepresentedbycylinder/head/sectorisalsocalledphysicaldiskaddress(2)asingledigitrepresentstherelativesectororDOSsector,alsoknownasthelogicalfancode(3)conversionformulabetweenrelativesectorandabsolutesector4.DOSpartitionofdiskareaAformattedharddisk,thediskaccordingtothedatarecordsofdifferentfunctioncanbedividedintothemainbootrecord(MBR:MainBootRecord),Dos(DBR:DosBootRecord)bootrecord,fileallocationtable(FAT:FileAssignTable),therootdirectory(BD:BootDirectory)andthedataarea.Thefirst5importantinformationontheoutertrackofthedisk,thereasonisthattheperimeteroftheouterringisgreaterthantheperimeteroftheinnerring,thatistosay,thestoragedensityoftheouterringissmallerandthereliabilityishigher.Mainpoints:(1)theentirediskcanbedividedintoMBR,DBR,FAT,BD,anddataareas.(2)MBR,DBR,FAT,andBDonthedisk.5.MBRMBRislocatedinthefirstphysicalsectoroftheharddisk(absolutesector),cylinder0,head0,sector1.SincetheDOSismadeupofcylinder0,head1,sector1,theMBRdoesnotbelongtotheDOSsector,andDOScannotbeaccesseddirectly.MBRcontainsthemainbootandharddiskpartitiontablesfortheharddisk.Thepartitiontablehas4partitionrecords.Arecordareaisatablethatrecordsinformationaboutpartitions.Itisstoredcontinuouslyfromthemainbootrecordoffsetaddress01BEH,eachrecordingareaof16bytes.FormatofpartitiontableTheoffsetmeaningofapartitionedtableentry00bootdesignator1BTheheadnumberofthe01partitionbootrecord1BThe02partitionguidesthesectorandcylindernumber2Boftherecord04systemdesignator1B05endofpartitionheadnumber1B06partitionendsectorandcylindernumber2BThenumberofsectorsinfrontofthe08partition4BThetotalnumberofsectorsinthe0Cpartition4BOnly4partitionshave1activepartition,namelyC.Thesymbolis80Hinthefirstbyteofthepartitionedtable.If00H,inactivepartitionsareindicated.Suchas:80010100,0B,FE,3F,81,3F,000000,C3,DD,1F,00,FE,BF,0C,02,DE,1F,00,0E,9061000000,00000000,0000Mainpoints:(1)MBRislocatedinthefirstphysicalsectorofcylinder,cylinder0,head0,sector1.NotpartoftheDOSsector,(2)themasterbootrecordisdividedintothemainbootprogramandtheharddiskpartitiontableoftheharddisk.6.DBRDBRislocatedincylinder0,head1,sector1,logicalsector0.DBRisdividedintotwoparts:theDOSbootstrapprogramandtheBPB(BIOSparameterblock).TheDOSbootloadercompletesthelocationandloadingoftheDOSsystemfiles(IO.SYS,MSDOS.SYS),whiletheBPBisusedtodescribediskinformationfortheDOSpartition.BPBislocatedatDBRoffset0BH,withatotalof13bytes.ItcontainslogicalformattingparametersusedforcomputingDOS,fileallocationtableondisk,startaddressdirectoryareaanddataarea,BPBafterthreewords(grid)toprovidephysicalformatwithsomeparameters.Thebootprogramordevicedriverconvertsthedisklogicaladdress(DOS,areacode)intophysicaladdresses(absolutefannumbers)basedonthisinformation.BPBformatSerialoffsetaddressmeaning103H0AHNo.OEM20BH-0CHbytespersector30DHperclustersectornumber40EH0FHretainthenumberofsectors510HFATbackupnumber611H12Hrootnumber713H-14Hdisktotalsectorcount815Hdescriptionmedium916H17HsectorsperFAT1018H19Hsectorspertrack111AH1BHhead121CH1FHspecialhiddensectors1320H23Htotalsectorcount1424H25Hphysicaldrivenumber1526Hextendedbootvisa1627H2AHvolumeserialnumber172BH35Hvolumelabel1836H3DHfilesystem.DOSbootrecordformula:ThefileallocationtableandkeepthenumberofsectorsThenumberofrootdirectory=xFATreservedsectorofeachFATsectorThedataareaandtherootdirectoryofthelogicalsectornumber(32+X+(directoryintherootdirectoryofthenumberofbytespersector1bytespersector))DIVAbsolutesectornumber=logicalsectornumber+hiddensectornumberSectornumber=(absolutesectornumberMODthenumberofsectorspertrack)+1Headnumber(DIV=absolutesectornumberofsectorspertrack)headnumberMODTracknumber(DIV=absolutesectornumberofsectorspertrack)headnumberDIVMainpoints:(1)DBRislocatedincylinder0,head1,sector1,anditslogicalareacodeis0(2)DBRcontainstheDOSbootprogramandtheBPB.(3)BPBisveryimportant,sothatthelogicaladdressandphysicaladdresscanbecalculated.SevenThedirectoryfilename,thefirstbyteinthearea,hasaspecialmeaning:00Hstandsforunused05Hs