硬盘结构及基本知识.ppt

ByPatiwatKamonpet BasicDiscDrive DiscDriveOverviewDiscDriveBasicsMagneticRecordingBasicsRecordingChannel ComputerSystem DiscDriveOverview Today sPCArchitecture IOBusLogic ISABus Otherperipherals CPUPentiumPro Memory PCIBridgeChip VideoGraphicsAdapterCard InterfaceAdapterCard Monitor IDEorSCSIDiscDrive Cable RibbonCable PCIBoardEdgeConnection PCIBoardEdgeConnection PCIBus LocalSystemBus WiredonMotherBoard WiredonMotherBoard WiredonMotherBoard Files CollectionofBytesTextDocumentComputerInstructionsPictureetc SequenceofBlocks Storedin Fileisreferencedbyafilenameratherthanlocationondisk Filesaremanagedbythecomputer soperatingsystem Thediskdrivehasnoawarenessoffiles StoringFilesonDiscDrive Computer DiscDrive Hereare3BlockofDataStartStoringinLocation5 Controller InterfaceAdapter File Letter DOC LETTWR DOC ANOTHER DOC 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 DIRECTORY TransferRateinMegaMytespersecond MBps HowtoAccessFiles Directory AListofFilenamesandLacations FilenameLETTER DOCPROGRAM EXEANOTHER DOC Blocklocationondisk 5 6 7 1024 1025 1026 1027 12 13 14 15 16 Theoperatingsysteminthecomputerkeepstrackofthedirectory InDOS thedirectorykeepstrackofthelocationforonlythe1stblockofeachfile TheFileAllocationTable orFAT keepstrackofthelocationoftheotherblocks HDAComponents DISC CIRCULATEFILTER CLAMPRING ODLIMITSTOP BOTTOMPOLE VCM PCC PREAMPCHIP IDLIMITSTOP HEAD FLEXURE ARM PIVOTCARTRIDGEBEARING TOPVIEW DiscDriveBasics PCBComponents HOSTCONTROLLER VCM SPINDLECONTROLLER READ WRITECHANNEL MICROCONTROLLER SERVOCONTROLLER SRAM DRAM SHOCKSENSOR SPINDLECONNECTOR HDACONNECTOR SHOCKIC MassStorageArchitectureUsingDiscDrives Read WriteChannel PositionSystem SPMControl SpindleMotor VCM VoiceCoilMotor Controller InterfaceAdapter Memory CPU PC ATSystemBus ISA SCSIRibbonCable Embebbedonmotherboardoradd incard BlockDefinitions UsingRecordingHeadToMagnetizeAFilm FilmMotion Current Magnetized NotMagnetized N S WritingDataOnAMagneticFilm FilmMotion CurrentReversed TransitionResults S N Track Track AstripofdatawrittenonamagneticfilmEachbit svalueissampledatregularinterval 1whenmagnetictransitionpresents0whenmagnetictransitiondoesnotpresent TrackWidth 0 1 0 0 1 1 1 SamplingPeriod WriteOtherTracksbyMovingtheHead 0 0 0 0 0 1 1 1 1 1 1 1 1 FilmMotion TrackDensity TrackWidth TrackPitch TrackDensity Numberoftracksthatfitinoneinch TPI BitDensity LinearDensity BitLength BitDensity Numberofbitsthatfitinoneinchoftrack BPI ArialDensity 1 1 ArealDensity Theamountofdatathatcanbestoredin1squareinch AD BPI TPI ReadingDataBackbyMRReadHead 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 0 0 0 RunconstantcurrentthroughMRstripe Measuretheresistance Magneticfieldfromfilmpickedupbystripe Fieldvariationinstripechangestheresistance MRstandsforMagnetoResistance FilmMotion ProblemwithMRStripe TheMRstripedetectsthefieldfromatransitionalongwayaway Solutions SpacethetransitionsfarapartDetectseveraloverlappingbitsatatimeUseshields ShieldedMRHead ShieldspermitonlytheMRstripetoonly see themediabelowthegap TheVoltageBeingPickedUpisNotVeryHigh Preamp WallPlug220VoltsComputerSignals3 5VoltsFlashlightBattery1 5VoltsEKGwavesonyourskin0 01VoltsTVSignal pickedupbyantenna 0 0008VoltsSignalFromRecordingHead0 0003Volts 0 0003V 0 075V Pre amplifythereadsignalveryclosetothehead x250 InductiveWriteMRReadHead IntegratedInductiveWriteMRReadHead TrackWidth ReaderGap MagneticSpacing HeadWidth Trackwidthisdeterminedbyheadwidth approximatelyequal Bitlengthisdeterminedbyreadergapandspacingfromgaptomediaandmanyothers WhatControlsDensity TherateatwhichdataisreadorwrittenthroughtheheadmeasuredinMillionbitspersecond Mbps AsBitDensityIncreases SoDoesDataRate Don tconfusedataratewithtransferrate therateatwhichdatatransfersovertheinterface inMegabytespersecondorMBps FilmMotion DataRate MagneticStorageOnADiscDrive CircularTracks VoiceCoilMotormovestheheadinandout SpindleMotordrivesthediscatconstantRPM CalculateDataRate r 0 9 r 1 8for3 5 media DataRate BitDensityxVelocity bits sec bits inch inch sec DR BPIx RPM 60 x2 r Circumferenceatouteredge 2 r 11 3inchesVelocity CircumferencexRotationRateVelocity 11 3inches revx5400rpmx 1 60 min secVelocity 1017inches secDataRate 180Kbpix1017inches sec 183Mbps 5400rpmBPI 180k Sectors 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 0 20 21 22 23 24 25 26 27 28 29 30 31 Diskdrivestoreover100 000bytesinatrack ToobigtodealwithWebreakeachtrackintochunkscalledsectors MostcommonsectorSize 512Bytes 1024and2048bytescommon TypicalSectorsPerTrack 50to256 determinedbybitdensity Breakingtracksintosectorsusedupsomespace FormattingEfficiency 5 15 ConstantAngularRecording CAR ZoneBitRecording BPI Velocity DataRate Zone MaximizeCapacity Zone ZoneTable ConstantAngularRecordingCapacity Capacity numberoftracks bitspertracknumberoftracks TPI Rod Rid bitspertrack BPI Rid 2 RidCaptacity TPI Rod Rid bitspertrack ConstantAngularRecordingbitspertrack constant Rid Rod Radius bitspertrack Area Zoning MaxCapacity ZonedRecordingbitspertrack 2 r BPI 50 for3 5 FF Zoning PracticalCapacity Rid Rod Radius bitspertrack 1 N 1 N numberofzones 4inthisexample 4zones 38 improvement8zones 44 improvement4zones 47 improvement4zones 48 improvement Typicalzoneddrivehas16zones For3 5 FFdrives thelimittozoning simprovementisabout150 MagnetizationCurveofMedia Squareness Coercive Squareness Remanence Saturationmagnetization Coercivity SlopeatCoercivity MagneticRecordingBasics LongitudinalRecordingWriteField Head Head Hx 2000Oe Hx 2200Oe Linesofconstanthorizontalfieldintensity Gap 1800 2000 2200 2400 2600 2800 TheWriteBubble InsidewritebubbleField Hcof2000OeStrongenoughtomagnetizemedia OutsidewritebubbleField Hcof2000OeStrongenoughtomagnetizemedia MediaLayerHc 2000Oe WritingaTransition Mediamotion TransitionwrittenatthetrailingEdgefothewritebubble Thisregionismagnetizedfirsttotheleftandthenagaintotheright WritingaTransition H M Mediamotion Themediainthisareasees1200Oeinthenewdirection Staysmagnetizedintheolddirection Themediainthisareasees2400Oeinthenewdirection Beingmagnetizedintheolddirection Hc M 0 RealTransitionsareBlurry H M Mediamotion IttakesdistanceonthemediatochangethedirectionofmagnetizationThisiscalled TransitionLength TransitionLength TransitionLength M Hh Hc x H M Hc x M Previousstateofmedium 50 50 Hd transitionlength 2a HorizontalComponentofHeadField DemagnetizationFieldfromtheTransition DemagnetizationFieldfromaTransition M Hd a transitionlengthparameter x Mr Arecordedtransitiongeneratesdemagnetizationfield Hd Williams ComstockModelofaRecordedTransition M Hd H Hc x H M Hc DH CalculatingTheTransitionLength TypicalValues FromWilliams ComstockModel WritingShorterSharperTransitions Mediamotion CloserHead MediaSpacing HMS ThinnerMediaLayerShorterWriteGapLengthTighterMediaSwitchingFieldDistribution allthemediaswitchatthesameH WriteFieldGradient MediaSquareness HighWriteFieldGradient closerbubbles H M TransitionLength HighMediaSquareness howsteepM Hcurve ReadingwithaGMRReadHead B M M B M M v v PhysicalMechanismofGMREffect M 3d Fermilevel M 4s Conductionband Twocurrentmodel FornormalGMRmaterials s dscatteringyieldsenergyloss significantlycontributestoresistivity Thenumberofavailable3dstatesatFermisurfaceisdifferentfordifferentspins PhysicalMechanismofGMREffect Highresistancestate Scatteringofspinelectronsoccurswithinamono layerfromtheinterface ParallelState AntiparallelState GMRReadHeadTransferCurve M2 M1 M2 M1 q Non magneticconductivelayer CharacterizingMagneticallyIsolatedPulses d T 2a PW50 G Where TransitionParameter Shield to ShieldSpacing MagneticSeparation MediaThickness FromWilliams Comstockmodel AchievingDesirableIsolatedPulses HighPeakAmplitudeIncreasefluxbyincreasingMr RemanenceMagnetization IncreasefluxbyincreasingmediathicknessDecreasemagneticspacingLongerreadgaplengthNarrowPulseWidthDecreasingmagneticspacingShortenreadgaplengthDecreasemediathicknessReduceself demagbyincreasingcoercivityIncreasewriteheadfieldgradientinheadconstruction don tusetoomuchcurrent reading writing Needtrade offs RecordingChannel RecordingChannel Channelwritedata Inputuserdata ECCencoder Channelencoder Equalizer Detector ECCdecoder Channeldecoder outputuserdata Analogreadbacksignal 10010110 110101101 1011011010 10010110 110101101 1011011010 DataWritingProcess writecurrent NRZI clock Data magneticmedium T DataReadingProcess SNSNSNSNSN I V T TheRead WriteChannel WriteCircuit Preamp Encoder Decoder ReadChannel DataToRecord WriteClock DataReadBack ReadRef Clock FromConroller ToConroller HDA PCB 20mA 200 Vpp 50mVpp TTL ECL TTL ECL Pre amp sWriteCircuit H BridgeDriver Vcc Rdamp Head Predriver WriteData WriteGate Pre amp sReadCircuit DifferentialPre amp V V Single ended Differential Common modenoiseisrejected Noise TheReadChannel SNSNSNSNSN Objective Outputadigitalpulsecorrespondingtothepeakofeachtransitiononthemedia MEDIA ReadSignal DerivedClock ReadChannelOutput T PeakDetector ThresholdDetector Differentiator ZeroCrossingDetector AND Read backpulse 1 0 1 Bitcell Bitcell Bitcell DetectionWindow T NeedtimingRecoverycircuit TimingRecovery PhaseLockedLoop PLL FromPeakdetector Clock PeakDetectorOutput VCOOutput VCOveryveryearly VCOveryearly VCOearly VCOslightlyearly VCOOnTime VCOslightlylate VCOlate PulseMissing VCOOnTime SlowDown SlowDown SlowDown SlowDown Don tChange SpeedUp SpeedUp Don tChange Don tChange PhaseDetectorOutput Inter SymbolInterference ISI LinearSuperpositionofpulsesReadbackWaveformWriteCurrent Pulsesinterferewitheachotherwhenwrittenclosetogether AmplitudesarereducedandTimingisdistortedUserDensity UD PW50 T T PW50 PeakDetectorOutputExamples PeakDetectionAnalogRead backWaveformThresholdDetectorOutputDifferentiatedDataZeroCrossingDetectorOutputDetectedData Read backWaveformsatDifferentUserDensities UD 0 75UD 1 5UD 2 0 AsynchronousDetection PeakDetection PLL DetectorhasNOknowledgeofthebittiming PLLknowsthebittimingNocommunicationtoDetector SynchronousDetection PeakDetection PLL Detectorhasknowledgeofwhenapulsemayoccur bittiming Canmakeahere not heredecisionMakesbetterdecisionsSignaltoNoiseRatio SNR canbelowerSampledDetectorallowsforpostcompensationModelandremoveISIasanerrorsource SynchronousChannel SampledPeakDetection 0 0 0 2 0 90 00 90 1 0 1 0 80 7 0 8 0 10 10 90 0 9 0 20 000 10100 11 10010 10000101001110010100 50 50 DetectionThreshold ReceivedSamples Targetvalues DetectedData SynchronousChannel SampledPeakDetection 50 50 DetectionThreshold 0 2 0 4 0 80 00 70 3 0 2 0 70 3 0 7 0 20 30 80 0 8 0 4 0 200 10100 10 10010 10000101001010010100 ReceivedSamples Targetvalues DetectedData Missing1transitionOrhaveonetoomanytransitions SequenceDetection Weknowcertainsequencesshouldn texist Makeuseofthefact Step1 DeterminetheruleforwhichsequencesexistForsampledpeakdetection polarityofpulsesmustalternateStep2 Comparetheobservedsampleswiththeexpectedsamplesfromallpossiblesequences Choosetheclosestsequence Closest sequencewithminimumsquarederrorClosest mostlikelysequence MaximumLikelihood Step1 RuleforPossibleSequences Preconditioned TheTrellis EachpaththroughthetrelliscorrespondstoapossibledatasequenceEachpaththroughthetrellispredictsapossiblesequenceofsamplestoobserves TrellisExample PRML PartialResponseMaximumLikelihoodBinarydatatransmissionmethodusedincommunicationssignalprocessingusedtodetectdatainanoisyenvironmentOriginallyusedwithdeepspaceprobesClass4appliedtomagneticrecordingchannels4inPR4referstotheclassofpartialresponsesystemusedformagneticrecordingchannelsTworelativelyindependentpartsPartialResponse MethodforequalizingthereadbacksignaltoachieveasampledthreeleveloutputMaximumLikelihood SequenceDetection PartialResponse Class4PartialResponseFilterorequalizeuntilatransitiongivesthefollowingwaveformTargetmorethanonenon zerosampleperpulseEachsampleonlycontainspartofthepulse response 2non zerosamples callthem 1 Allothersamples 0 PR4EqualizedIsolatedandDibitPulses IsolatedPulse DibitPulse ExampleClass4PartialResponseWaveform 00100000110101110010111011 NRZI PR4Eye pattern Allwaveformsatclockpointspassthroughoneofthreepointscorrespondingtosamplevaluesof 1 0 and1 Samplingonceeachbitperiodresultsinthreeleveloutput TrellisDiagramforClass4PartialResponse PR4StateDiagram Read backWaveformsatDifferentUserDensities UD 0 75UD 1 5UD 2 0 MagneticChannelSpectrum AtlowrecordingdensitiesthespectralenergyisconcentratednearonehalfofthechannelclockratefrequencyAthigherrecordingdensitiesmostofthesignalspectrumisbelowhalfofthechannelclockratefrequencyLimitchannelbandwidthto1 2Twithoutlosinginformation WhygotohigherorderPartialResponses PR4 PW50 T 0 5 EPR4 E2PR4 PRMLReadChannel AGC AutomaticGainControlmaintainsrequiredconstantsignallevel VGA GainControl LowPa