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1、CHAPTER7StorageHardDisksHardDisksLow-levelformat-organizesbothsidesofeachplatterintotracksandsectorstodefinewhereitemswillbestoredonthedisk.Partitioning:divideharddiskintoseparateareascalledpartitions;eachpartitionfunctionsasifitwereaseparateharddiskdrive.High-
2、levelformatdefinesthefileallocationtable(FAT)foreachpartition,whichisatableofinformationusedtolocatefilesonthedisk.HardDisksUsethicker,metallicplattersforstorageFasterthanafloppydisketteLargecapacitySensitiveinstrumentsLowLevelFormattingLowlevelformatscansdiskf
3、ordefectsandsetsasidesectorswithdefectssotheyarenotusedfordata.IDEdrivesshouldneverbelowlevelformattedbyauserortechnician.Onlyhighlevelformatnecessary.HardDriveFloppiesTwosizes3.5inch5.25inch3.5inchholds1.44MBforHighdensityand750KBforDoubleDensityConnectedwith3
4、4pinribboncableTwoFloppyDrivespossibleHastwistincabletodistinguishAdrivefromBdriveSCSIPronouncedScuzzySmallComputerSystemsInterfaceForwiderangeofperipheraldevices,includingharddisks,tapedrives,opticaldrives,CD-ROMsanddiskarrays.8devicescanconnecttoadaisychainTh
5、ischainmustbeterminatedatbothendsEachdeviceonchainisassigneduniquedeviceIDnumberthatisdeterminedbyjumpersorDIPswitchesInstallingandconfiguringSCSISCSIbussupports8devicesThereareeightSCSIIDsnumbered0through7ID7isalwaysreservedfortheSCSIhostadapterSCSIharddisk,if
6、usedasabootdrive,isassignedSCSIID0IfyouhavebothIDEandSCSIharddrive,IDEdriveshouldbebootdriveTypesofSCSIsSCSI1-5MBtransferrate,Centronics50pinorDB25,has8bitbusSCSI2-alsoSCSIFastWide,includes16bitbus,calledWideSCSI,andtwiceasfasttransferrateSCSI3-IncludesUltraSCS
7、I,WideUltraSCSI,andUltra2SCSI,16bitbuswithupto80MBpstransferrateRAIDRedundantArrayofIndependentDisksCategoryofdiskdrivesthatemploys2ormoredrivesincombinationforfaulttolerance(errorrecovery)10levelsofRAID3ontestwillbe:RAID0,RAID3,RAID5RAIDcontinuedRAID0-Stripedd
8、iskwithoutparityRAID3-ParalleltransferwithparityRAID5-DatastripingwithparityHowDataisOrganizedonDiskTracks-circularareasofthediskLengthofatrackonecircumferenceofdiskOver1000
