Domov Technika Skladovací systém

Skladovací systém



Úvod

Úložný systém v jedné z důležitých částí počítače. Úložný systém poskytuje možnost zapisovat a číst informace (programy a data), které počítač potřebuje k dosažení funkce paměti informací v počítači.

Thecoreofacomputerstoragesystemismemory,whichisanindispensablememorydeviceusedtostoreprogramsanddatainacomputer.

Interní paměť (zkrátka paměť) ukládá především programy a data, která počítač potřebuje pro aktuální práci, včetně vysokorychlostní mezipaměti (Cache, cache for short) a hlavní paměti. V současné době je hlavní součástí paměti polovodičová paměť. úložiště a polovodičové úložiště. Paměťová média zahrnují pevné disky, optické disky, pásky a mobilní úložiště.

Themulti-levelstoragearchitectureofmoderncomputersystemsisshowninFigure6-1.Thehigherthetop,theclosertotheCPU,thefasterthememory,thesmallerthecapacity,andthehigherthepriceperbit.Usingthisorganizationmethodcanbettersolvethecontradictionbetweenstoragecapacity,speedandcost,andprovidealayerofstoragethatislogicallyequivalenttothecheapestinpriceandcapacity,andtheaccessspeedisclosetothefastestinthestoragesystem.Storagesystemoflayeredmemory.

Development

Ifthecomputer'sexternalstoragesystemhasbeendevelopedsince1956whenIBMproducedthefirstharddisk,ithasbeendevelopedformorethanhalfacentury.Inthepasthalfcentury,storagemediaandstoragesystemshaveachievedgreatdevelopmentandprogress.

Intheearlydaysofdatastorage,devicessuchasdiskarraysweregenerallyusedasperipherals,andtheserversweredirectlyconnectedforstorage.Inrecentyears,withthedevelopmentofnetworktechnology,thedatareadingrangeoftheserverhasalsobeengreatlyexpanded,graduallyrealizingthecurrentnetworkstorage.Comparedwithtraditionalstorage,theadvantagesofnetworkstoragearemoreprominent.Itisnotonlyconvenienttoinstallandlowincost,butalsoabletoexpandstoragedevicesonalargescale,thuseffectivelymeetingthestoragespacerequirementsofmassivedatastorage.However,networkstorageconsumesalotofnetworkresources,whichisadifficultproblem.Forthisreason,SANstoragearchitecturegraduallyappeared.

Tradiční úložný systém

V současné době existují tři hlavní architektury tradičních úložných systémů, včetně DAS, NAS a SAN.

1.DAS(Direct-AttachedStorage,Direct-AttachedStorage)

Asthenameimplies,thisisastoragemethodinwhichstoragemediasuchasharddisksaredirectlyconnectedtothehostthroughabusadapter.Thereisusuallynonetworkequipmentinvolvedbetweenthestoragedeviceandthehost.ItcanbesaidthatDASisthemostprimitiveandbasicstoragearchitecture,anditisalsothemostcommononpersonalcomputersandservers.TheadvantagesofDASareitssimplestructure,lowcost,andhighefficiencyofreadingandwriting.Thedisadvantageisthatithaslimitedcapacityandisdifficulttoshare,whichmakesiteasytoform"informationislands."

2.NAS(Network-AttachedStorage,networkstoragesystem)

NASisanetworkstoragesystemthatprovidesfile-levelaccessinterfaces,usuallyusingnetworkfilessuchasNFS,SMB/CIFS,etc.Sharingagreementforfileaccess.NASsupportssimultaneousaccessbymultipleclientsandprovidesalarge-capacitycentralizedstoragefortheserver,whichalsofacilitatesdatasharingduringtheserviceperiod.

3.SAN(Síť úložiště, síť úložiště)

Setupadedicatedstoragenetworkbetweenserversandstoragedevicessuchasdiskarraysthroughhigh-speednetworkequipmentsuchasfiberswitchestoprovidehighperformanceStoragesystem.

ThedifferencebetweenSANandNASisthatitprovidesablock-levelaccessinterface,andgenerallydoesnotprovideafilesystematthesametime.Undernormalcircumstances,theserverneedstomaptheSANstoragetoalocaldiskthroughanaccessprotocolsuchasSCSI,anduseitaftercreatingafilesystemonit.Atpresent,mainstreamenterprise-levelNASorSANstorageproductscangenerallyprovideTB-levelstoragecapacity,andhigh-endstorageproductscanalsoprovideuptoseveralpetabytesofstoragecapacity.

Distributedstoragesystem

Bigdatahasledtoanexplosivegrowthintheamountofdata.Traditionalcentralizedstorage(suchasNASorSAN)can’tperformwellintermsofcapacityandperformance.Meettheneedsofbigdata.Therefore,distributedstoragewithexcellentscalabilityhasbecomethemainstreamarchitectureforbigdatastorage.Distributedstoragemostlyusesordinaryhardwareequipmentastheinfrastructure,sothestoragecostperunitcapacityisalsogreatlyreduced.Inaddition,distributedstoragealsohasdifferentdegreesofadvantagesintermsofperformance,maintainability,anddisastertolerance.

Thekeytechnicalissuesthatadistributedstoragesystemneedstosolveincludescalability,dataredundancy,dataconsistency,globalnamespacecaching,etc.Fromanarchitecturalpointofview,distributedstoragecanbedividedintoTherearetwotypes:C/S(ClientServer)architectureandP2P(Peer-to-Peer)architecture.Ofcourse,therearealsosomedistributedstoragesystemswherethesetwoarchitecturesexistatthesametime.

Anothercommonproblemfacedbydistributedstorageishowtoorganizeandmanagemembernodes,andhowtoestablishthemappingrelationshipbetweendataandnodes.Thedynamicincreaseordepartureofmembernodescanbasicallyberegardedasanormalstateinadistributedsystem.

TheCAPtheoryofdistributedsystemdesignproposedbyEricBrewerin2000pointedoutthatadistributedsystemcannotguaranteethethreeelementsofconsistency,availability,andpartitiontoleranceatthesametime.Therefore,anydistributedstoragesystemcanonlyoptimizetwoofitselementstothegreatestextentbasedonitsspecificbusinesscharacteristicsandspecificneeds.Ofcourse,inadditiontothethreedimensionsofconsistency,availability,andpartitiontolerance,adistributedstoragesystemoftenhasdifferenttrade-offsinfeaturedesignaccordingtospecificservices,suchaswhetheritneedsacachemoduleandwhetheritsupportscommonfiles.Systeminterface,etc.

Cloudstorage

Cloudstorageisanonlinestoragesystemprovidedbythird-partyoperators,suchasonlinestoragesystemsforindividualusersandfile,blockorobjectstoragesystemsforenterprises,etc..Cloudstorageoperatorsareresponsibleforthedeployment,operation,andmaintenanceofdatacenters,andprovidedatastoragepackagestocustomersintheformofservices.Asoneoftheextensionsandimportantcomponentsofcloudcomputing,cloudstorageprovidesdatastorageservicesof"distributionondemandandbillingbyvolume".Therefore,usersofcloudstoragedonotneedtobuildtheirowndatacentersandinfrastructure,nordotheyneedtocareaboutthemanagementandmaintenanceoftheunderlyingstoragesystem,andcandynamicallyexpandorreducetheirdemandforstoragecapacityaccordingtotheirbusinessneeds.

Cloudstorageusesoperatorstocentrallyanduniformlydeployandmanagestoragesystems,whichreducesthecostofdatastorage,therebyloweringthebarrierstoentryforthebigdataindustry,andhelpingsmallandmedium-sizedenterprisestoenterthebigdataindustry.Providespossibilities.Forexample,thewell-knownonlinefilestorageserviceproviderDropboxisbasedontheonlinestoragesystemS3providedbyAWS(AmazonWebServices).Beforetheriseofcloudstorage,itwasalmostimpossibletostartastartuplikeDropbox.

Thestoragesystemsusedbehindcloudstorageactuallymostlyusedistributedarchitecture,andcloudstoragehasalsoencounterednewproblemsandrequirementsindesignduetoitsmorenewapplicationscenarios.Forexample,cloudstoragemostlyneedstosolvehowtosupportmulti-tenantaccessinthemanagementsystemandaccessinterface.Inamulti-tenantenvironment,itisinevitabletosolveaseriesofproblemssuchassecurityandperformanceisolation.Inaddition,cloudstorageisthesameascloudcomputing.Acommonproblemthatneedstobesolvedistheissueoftrust—howtotechnicallyensuretheprivacyandsecurityofenterprisebusinessdataonthethird-partystorageserviceproviderplatform.Itisatechnicalchallengethatmustbesolved.

Storageisprovidedtousersintheformofservices,andcloudstoragegenerallyadherestothecharacteristicsofsimplicityandeaseofuseintheaccessinterface.Forexample,Amazon'sS3storageaccessesdatathroughastandardHTTPprotocolandasimpleRESTinterface.UsersuseHTTPmethodssuchasGet,Put,andDeletetoobtain,store,anddeletedatablocks.Forthesakeofeaseofoperation,AmazonS3servicedoesnotprovideoperationssuchasmodificationorrenaming;atthesametime,AmazonS3servicedoesnotprovideacomplexdatadirectorystructurebutonlyprovidesaverysimplehierarchicalrelationship;userscancreatetheirownDatabucket(bucket),andalldataisstoreddirectlyinthisbucket.Inaddition,cloudstoragehastosolvetheproblemofusersharing.ThedatainAmazonS3storageisdirectlyaccessedandidentifiedthroughauniqueURL.Therefore,aslongasotherusersareauthorized,theycanaccessthroughtheURLofthedata.

Storagevirtualizationisanimportanttechnicalfoundationofcloudstorage.Itisatechnologythatunifiesmultipleisolatedstoragesystemsintoanabstractresourcepoolbyabstractingandencapsulatingthephysicalcharacteristicsoftheunderlyingstoragesystem.Throughstoragevirtualizationtechnology,cloudstoragecanachievemanynewfeatures.Forexample,thelogicalisolationofuserdata,thestreamlinedconfigurationofstoragespace,etc.

Hierarchicalstructure

Thehierarchicalstructureofthestoragesystemcanbedividedintofivelevels:registerset,cache,mainmemory,virtualmemoryandexternalmemory.Amongthem,theregistergroupisalwaysinsidetheCPU,andtheprogrammercanaccessitthroughtheregistername.Thereisnobusoperation,andtheaccessspeedisthefastest;theremaining4levelsarealloutsidetheCPU.Cacheandmainmemoryconstitutetheinternalstoragesystem,andtheprogrammercanaddressthroughthebus.Theaccessspeedofthememoryunitisworsethanthatoftheregister;thevirtualmemoryistransparenttotheprogrammer;theexternalstoragesystemhasalargecapacityandneedstoexchangedatawiththeCPUthroughtheI/Ointerface,andtheaccessspeedistheslowest.

Cachememory

Původní význam mezipaměti (Cache) označuje typ RAM, který je rychlejší přístupovou rychlostí než obecná paměť s náhodným přístupem (RAM). Obecně řečeno, nepoužívá technologii dynamické paměti náhodného přístupu (DARM), jako je hlavní paměť systému (S, ale používá technologii RAM) extenzivní paměti RAM

Thehigh-speedbuffermemoryisaprimarymemorybetweenthemainmemoryandtheCPU.Itiscomposedofastaticmemorychip(SRAM).Ithasasmallcapacitybutamuchfasterspeedthanthemainmemory.ItsmostimportantindicatorIsitshitrate.Theschedulingandtransferofinformationbetweenthecachememoryandthemainmemoryareautomaticallyperformedbythehardware.

Struktura kompozice

Thecachememoryismainlycomposedofthefollowingthreeparts:

  1. Cachememorybank: Uložte instrukce a data přenesená z hlavní paměti.Systém úložiště

  2. Komponenta převodu adresy: Vytvořte tabulku adresářů, abyste převedli adresu hlavní paměti na adresu hlavy cacu.

  3. Nahradit komponentu: Když je mezipaměť plná, proveďte výměnu dat v souladu s jistou strategií a upravte tabulku adresáře v komponentě překladu hlav.

Princip práce

High-speedmemoryisusuallycomposedofhigh-speedmemory,Lenovomemory,replacementlogiccircuitandcorrespondingcontrolcircuitcomposition.Inacomputersystemwithacachememory,theaddressoftheprocessortoaccessthemainmemoryisdividedintothreefields:rownumber,columnnumber,andgroupaddress.Therefore,themainmemoryislogicallydividedintoseveralrows:eachrowisdividedintoseveralmemorycellgroups;eachgroupcontainsseveralordozensofwords.High-speedmemoryisalsodividedintorowsandcolumnsofmemorycellgroupsaccordingly.Bothhavethesamenumberofcolumnsandthesamegroupsize,butthenumberofrowsinthehigh-speedmemoryismuchsmallerthanthatinthemainmemory.

Lenovomemoryisusedforaddressassociationandhasstorageunitswiththesamenumberofrowsandcolumnsashigh-speedmemory.Whenamemorycellgroupinacertaincolumnandrowofthemainmemoryistransferredtoanemptymemorycellgroupinthesamecolumnofthehigh-speedmemory,thememorycellcorrespondingtotheLenovomemoryrecordstherownumberofthetransferredmemorycellgroupinthemainmemory.

Whentheprocessoraccessesthemainmemory,thehardwarefirstautomaticallydecodesthecolumnnumberfieldoftheaccessaddress,soastocombinealltherownumbersoftheLenovomemorywiththerownumberofthemainmemoryaddressFieldsarecompared.Iftheyarethesame,itindicatesthatthemainmemoryunittobeaccessedisalreadyinthehigh-speedmemory,whichiscalledahit.Thehardwaremapstheaddressofthemainmemorytotheaddressofthehigh-speedmemoryandexecutestheaccessoperation;iftheyarenotthesame,thenIndicatesthattheunitisnotinthehigh-speedmemory,whichiscalledfailure.Thehardwarewillperformtheoperationofaccessingthemainmemoryandautomaticallytransferthemainmemorycellgroupwheretheunitislocatedintotheemptymemorycellgroupinthesamecolumnofthehigh-speedmemory.TherownumberofthegroupinthemainmemoryisstoredintheunitatthecorrespondinglocationoftheLenovomemory.

Whenafailureoccursandthereisnoemptypositioninthecorrespondingcolumnofthehigh-speedmemory,acertaingroupinthecolumniseliminatedtomakeroomforthenewlytransferredgroup,whichiscalledreplacement.Therulesfordeterminingreplacementarecalledreplacementalgorithms.Commonlyusedreplacementalgorithmsincludeleastrecentlyusedalgorithm(LRU),first-infirst-outmethod(FIFO),andrandommethod(RAND).Thereplacementlogiccircuitperformsthisfunction.Inaddition,whenperformingawriteoperationtothemainmemory,inordertomaintaintheconsistencyofthecontentsofthemainmemoryandthehigh-speedmemory,thehitsandfailuresarehandledseparately.

Mapování adres a konverze

Addressmappingreferstothecorrespondencebetweentheaddressofacertaindatainthemainmemoryandtheaddressinthecacherelation.Herearethreeaddressmappingmethods:

1.Plně asociativní metoda

Theaddressmappingruleofthefully-associatedmethodis:anypieceofthemainmemorycanbemappedtotheCacheAnypiece.Thebasicrealizationideais:1)Themainmemoryandthecachearedividedintodatablocksofthesamesize;2)Acertaindatablockofthemainmemorycanbeloadedintoanyspaceofthecache.

ThedirectorytableisstoredinLenovomemoryandconsistsofthreeparts:theblockaddressofthedatablockinthemainmemory,theblockaddressafterstoringitinthecache,andtheeffectivebit(alsocalledtheloadbit).Sinceitisafullyassociativemethod,thecapacityofthedirectorytableshouldbethesameasthenumberofblocksinthecache.

Theadvantageofthefullassociativemethodisthatthehitrateisrelativelyhigh,andtheCachestoragespaceutilizationrateishigh;thedisadvantageisthatwhenaccessingtherelatedmemory,itmustbecomparedwiththeentirecontenteverytime,andthespeedislowandthecostishigh.Lessapplications.

2.Directassociativní metoda

TheaddressmappingruleofthedirectassociativemethodisthatablockinthemainmemorycanonlybemappedtoaspecificblockintheCache.Thebasicrealizationideais:

1)Hlavní paměť a cache jsou rozděleny do datových bloků stejné velikosti;

2)Themainmemorycapacityshouldbeanintegermultipleofthecachecapacity,andthemainmemoryspaceDivideintoareasaccordingtothecachecapacity,thenumberofblocksineachareaof​​themainmemoryisequaltothetotalnumberofblocksinthecache;

3)AblockofthemainmemorycanonlybestoredinthecachewhenitisstoredinthecachePositionwiththesameblocknumber.

Datablockswiththesameblocknumberineachareaof​​themainmemorycanbetransferredtotheaddresswiththesameblocknumberinthecache,butonlyoneblockcanbestoredinthecacheatthesametime.Sincethetwofieldsofthemainblocknumberandthecacheblocknumberandtheaddressintheblockarecompletelythesame,onlytheareacodeofthetransferredblockcanberecordedwhenthedirectoryisregistered.Thedirectorytableisstoredinhigh-speedandsmall-capacitymemory,andincludestwofields:theareanumberofthedatablockinthemainmemoryandtheeffectivebit.Thecapacityofthedirectorytableisthesameasthenumberofcachedblocks.

Theadvantageofthedirectassociativemethodisthattheaddressmappingmethodissimple.Whenaccessingdata,youonlyneedtocheckwhethertheareacodeisequal,soyoucangetfasteraccessspeedandsimplehardwareequipment;thedisadvantageisthereplacementoperationFrequent,thehitrateisrelativelylow.

3.Metoda skupinového asociativního mapování

Theaddressmappingruleofthegroup-associativemappingmethodisthatablockinthemainmemorycanonlybestoredinanyblockofthesamegroupnumberinthecache.Thebasicrealizationideais:

1)Hlavní paměť a mezipaměť jsou rozděleny do bloků podle stejné velikosti;

2)Hlavní paměť a mezipaměť jsou rozděleny do skupin podle stejné velikosti:

3)Themainmemorycapacityisanintegermultipleofthecachecapacity.Themainmemoryspaceisdividedintoareasaccordingtothesizeofthecachearea.Thenumberofgroupsineachareaof​​themainmemoryisthesameasthenumberofgroupsinthecache;

4)Whenthedatainthemainmemoryistransferredtothecache,thegroupnumbersofthemainmemoryandthecacheshouldbeequal,thatis,ablockineachareacanonlybestoredinthespaceofthesamegroupnumberinthecache,buttheblocksinthegroupcanbearbitrarilyStorage,thatis,thedirectmappingmethodisadoptedfromthegroupinthemainmemorytothegroupinthecache:afullyassociativemappingmethodisadoptedinthetwocorrespondinggroups.

Theconversionbetweenthemainmemoryaddressandthecacheaddressconsistsoftwoparts:thegroupaddressadoptsthedirectmappingmethodandisaccessedbyaddress;whiletheblockaddressadoptsthefullyassociativemethodandisaccessedbycontent.

Theadvantageofthegroupassociativemappingmethodisthatthecollisionprobabilityoftheblockisrelativelylow,theutilizationrateoftheblockisgreatlyimproved,andthefailurerateoftheblockissignificantlyreduced:thedisadvantageisthatthedifficultyandcostofimplementationarehigherthanthatofthedirectmappingmethod..

Memory

Memory(Memory),alsoknownasinternalmemoryormainmemory,ismadeofsemiconductordevices.ItisoneoftheimportantpartsofacomputerandisdirectlyaddressablebytheCPU.Thestoragespaceischaracterizedbyfastaccessspeed.Allprogramsinthecomputerareruninthememory,sotheperformanceofthememoryhasagreatimpactonthecomputer.ThefunctionofthememoryistotemporarilystorethearithmeticdataintheCPUandthedataexchangedwithexternalstoragesuchasharddisks.Aslongasthecomputerisrunning,theCPUwilltransferthedatathatneedstobecalculatedintothememoryforcalculation,andwhenthecalculationiscompleted,theCPUwilltransmittheresult.

Theprogramsweusuallyuse,suchasWindowsoperatingsystem,typingsoftware,gamesoftware,etc.,aregenerallyinstalledonexternalstoragesuchasharddisks,buttheirfunctionscannotbeusedalone.TheymustbeinstalledOnlywhenitisloadedintothememorytorun,canwereallyuseitsfunctions.Weusuallyenteraparagraphoftextorplayagame,infact,itisalldoneinthememory.Justlikeinastudyroom,thebookshelvesandbookcasesstoringbooksareequivalenttotheexternalstorageofthecomputer,andthedeskwhereweworkisthememory.Usuallywestorealargeamountofdatatobestoredpermanentlyonexternalmemory,andputsometemporaryorasmallamountofdataandprogramsinthememory.Ofcourse,theperformanceofthememorywilldirectlyaffecttheoperatingspeedofthecomputer.

Paměť zahrnuje dva typy paměti pouze pro čtení (ROM) a paměti s náhodným přístupem (RAM).

Paměť pouze pro čtení (ROM)

Paměť pouze pro čtení je ROM (ReadOnlyMemory)). Když je ROM vyrobena, informace (data nebo program) jsou uloženy a trvale uloženy. Informace lze pouze číst, nikoli zapisovat, a data nebudou ztracena, i když je stroj vypnutý. (DIP)integrovaný blok.

RandomAccessMemory (RAM)

RandomAccessMemoryisRAM(RandomAccessMemory),whichmeansthatdatacanbereadfromorwrittento.Whenthepowerofthemachineisturnedoff,thedatastoredinitwillbelost.Thememorymodule(SIMM)thatweusuallybuyorupgradeisusedasthecomputer'smemory.ItisasmallcircuitboardthatintegratestheRAMintegratedblockandplugsitintothememoryslotinthecomputertoreducetheRAMintegratedblockoccupancySpace.

Finallyintroducethetwoconceptsofphysicalmemoryandstorageaddressspace.Theyaretwodifferentconcepts,butbecausethereisaverycloserelationshipbetweenthetwo,andtheybothuseB,KB,MB,andGBtomeasuretheircapacity,itiseasytocauseconfusion.Physicalmemoryreferstoaspecificmemorychipthatactuallyexists.Forexample,thememorybarinstalledonthemotherboardandtheROMchiploadedwiththesystemBIOS,thedisplayRAMchiponthedisplaycardandtheROMchiploadedwiththedisplayBIOS,andtheRAMchipsandROMchipsonvariousadaptercardsareallphysicalmemories.Thestorageaddressspacereferstotherangeofmemoryencoding(encodingaddress).Theso-calledencodingistoassignanumbertoeachphysicalstorageunit(abyte),usuallycalled"addressing".Thepurposeofassigninganumbertoastorageunitistofinditeasilyandcompletethereadingandwritingofdata.Thisistheso-called"addressing",sosomepeoplealsocallthestorageaddressspaceaddressingspace.

Thesizeofthestorageaddressspaceandthesizeofthephysicalmemoryarenotnecessarilyequal.Letmegiveanexampletoillustratethisproblem:Thereare17roomsonafloor,andtheirnumbersare801~817.These17roomsarephysical,andtheiraddressspaceusesathree-digitcode,rangingfrom800to899,atotalof100addresses.Itcanbeseenthattheaddressspaceislargerthantheactualnumberofrooms.Formicrocomputersabove386,theaddressbusis32bits,sotheaddressspacecanreach2B,thatis,4GB.

Nevolatilní paměť (NVM)

Thenon-volatilememory(Non-Volatilememory,NVM)thathasappearedinrecentyearsischaracterizedbyitshighintegrationFeaturessuchashighspeed,lowenergyconsumption,non-volatility,andbyteaddressinghavereceivedwidespreadattention.Academiaandindustryhavedevelopedsomenewnon-volatilestoragemediaandtechnologies,suchasMagneticRAM(MRAM),SpinTransferTorqueRAM(STT-RAM),andPhaseChangeMemory(PhaseChangeMemory,PCM),resistiveRAM(RRAM),ferroelectricRAM(FerroelectricRAM,FeRAM),etc.Themainparametersofseveralmainstreamnewstoragedevicesarelistedinthetable.Itcanbeseenfromthetablethatnon-volatilestoragehasgoodperformanceintermsofintegrationandreadspeed,andisacandidateforconstructingpotentialnewstoragedevices.However,non-volatilestoragealsohasseveralobviousshortcomings:1)Ithasalargewritedelay,whichisanorderofmagnitudelargerthanthecorrespondingstoragemedium,andthewritedelayisgreaterthanthereaddelay,thatis,readandwriteareinconsistent.2)Althoughthereadoperationofnon-volatilestorageisfasterthanthewriteoperation,itisstillslowerthanthereadoperationoftraditionalstoragemedia;3)Thewritelifeofnon-volatilestorageislimited.Inthecaseofcontinuouswriting,thestorageunitisveryItwillsoonexpire.

Disk

Diskisthemostcommonlyusedexternalstorage.Itisaroundmagneticdiskpackedinasquaresealedbox.ThepurposeofthisistopreventthediskThesurfaceisscratched,causingdataloss.Thedatainformationstoredonthediskcanbestoredforalongtimeandcanbeusedrepeatedly.Disksaredividedintofloppydisksandharddisks.Atpresent,floppydiskshavebeenbasicallyeliminated.Computerswidelyuseharddisks.Wecancompareittoalargewarehouseforcomputerstostoredataandinformation.

Typy a složení pevných disků

ThetypesofharddisksmainlyincludeSCSI,IDE,andthepopularSATA.Therearecertainstandardsfortheproductionofanykindofharddisk.Withtheupgradeofthecorrespondingstandard,theharddiskproductiontechnologyisalsoupgrading.Forexample,theSCSIstandardhasgonethroughSCSI-1,SCSI-2andSCSI-3.Atpresent,weoftenvisitthewebsiteTheUltral-160seenbytheserverisbasedontheSCSI-3standard.IDEfollowstheATAstandard,andthecurrentpopularSATAisanupgradedversionoftheATAstandard.IDEisaparallelportdevice,whileSATAisaserialport.SATAwasdevelopedtoreplaceIDE.

Obecně řečeno, bez ohledu na to, jaký druh pevných disků se skládá z disku, hlavy, vřetena, řídicího motoru, řídicí jednotky hlavy, převodníku dat, rozhraní, mezipaměti atd.

TheharddiskstructureisshowninFigure2-6.Alldiscsarefixedonarotatingshaft,whichisthediscspindle.Allthediscsareabsolutelyparallel.Thereisamagneticheadonthestoragesurfaceofeachdisc,andthedistancebetweenthemagneticheadandthediscissmallerthanthediameterofthehair.Alltheheadsareconnectedtoaheadcontroller,andtheheadcontrollerisresponsibleforthemovementofeachhead.Themagneticheadcanmoveradiallyalongtheradiusofthedisc(actuallyitisanobliquetangentialmovement).Eachmagneticheadmustalsobecoaxialatthesametime,thatis,whenviewedfromdirectlyabove,allmagneticheadsoverlapatalltimes(However,thereisalreadyamulti-headindependenttechnology,whichisnotsubjecttothislimitation).Thediscrotatesatahighspeedataspeedofthousandsofrevolutionsperminutetotensofthousandsofrevolutionsperminute,sothatthemagneticheadcanreadandwritedataataspecifiedlocationonthedisc.

Princip práce pevných disků

1.Povrch disku

Thedisksofharddisksgenerallyusealuminumalloymaterialsasthesubstrate,high-speedharddisksItisalsopossibletouseglassasthesubstrate.Eachdiskofaharddiskhastwosides,namelytheupperandlowersides.Generally,eachsidewillbeusedtostoredataandbecomeaneffectivedisksurface.Therearealsoveryfewharddiskswithoddnumberofsides.Eachsucheffectivediskhasadisknumber,whichisnumberedsequentiallyfromtoptobottom,startingfrom0.Intheharddisksystem,thedisksurfacenumberisalsocalledtheheadnumber,becauseeachvaliddisksurfacehasacorrespondingreadandwritehead.Thedisksetofharddiskshas2to14platters,usually2to3platters,sothediskfacenumber(headnumber)is0~3or0~5.

2. Sledovat

Thediskisdividedintomanyconcentriccirclesduringlow-levelformatting.Theseconcentriccircletracksarecalledtracks,andinformationisrecordedonthesetracksintheformofpulsetrains.middle.Thetracksarenumberedsequentiallyfromtheoutsidetotheinside,startingfrom0.Eachharddiskhas300~1024tracksoneachsurface,andthenewlarge-capacityharddiskhasmoretracksoneachsurface.Eachtrackdoesnotrecorddatacontinuously,butisdividedintosegmentsofarcs.Theangularvelocitiesofthesearcsarethesame,butbecausetheradiallengthisdifferent,thelinearvelocityisalsodifferent.Thelinearvelocityoftheouterringishigherthanthatoftheinnerring.Thelinearvelocityislarge,thatis,underthesamerotationspeed,thelengthofthearcdrawnbytheouterringinthesameperiodoftimeisgreaterthanthelengthofthearcdrawnbytheinnerring.Eacharciscalledasector,andsectorsarenumberedstartingfrom1,andthedataineachsectorisreadorwrittenasaunitatthesametime.Thetracksareinvisible,justsomemagnetizedareasonthedisksurfacethataremagnetizedinaspecialway,andtheplanninghasbeencompletedwhenthediskisformatted.

3. Válec

Thesametrackonalldisksformsacylinder,usuallycalledacylinder.Themagneticheadoneachcylindergoesfromtoptobottomandfrom0Startnumbering.Datareading/writingisperformedonacylinder,thatis,whentheheadreads/writesdata,theoperationstartsfromhead0inthesamecylinder,andthenoperatesondifferentdisksurfacesofthesamecylinder,thatis,thehead,onlyinthesamecylinder.Afterallthemagneticheadsonthesurfacehavebeenread/written,themagneticheadtransferstothenextcylinder(thecylinderthatisconcentricandtheninward),becausetheselectionofthemagneticheadonlyneedstobeswitchedelectronically,andtheselectionofthecylindermustbemechanicallySwitching,thespeedoftheheadmovingtotheadjacenttrackduringelectronicswitchingismuchfasterthanthatduringmechanicalswitching.Therefore,datareading/writingisperformedonthecylinderinsteadofthedisksurface,therebyimprovingtheread/writeefficiencyoftheharddisk.

Thenumberofcylindersofaharddiskdrive(orthenumberoftracksperdisk)dependsonthewidthofeachtrack(alsorelatedtothesizeofthehead),andalsodependsonthepositioningmechanismThesizeofthestepbetweentracks.

4. Sektor

Theoperatingsystemstoresinformationontheharddiskintheformofsectors(Sector).Eachsectorincludestwomainparts:sectoridentifierandstorageThedatasegmentofthedata(usually512B).

Identifikátor sektoru, také nazývaný hlavička sektoru, zahrnuje tři čísla, která tvoří trojrozměrnou adresu sektoru:1)Číslo disku:hlava(nebo disk),kde je sektorumístěný2)Číslo válce:Track,určetesměrradiáluhlavy:3)Číslosektoru:Data na dráze,které se také nazývá.

Thesectorheaderalsoincludesafield,inwhichthereisamarkthatidentifieswhetherthesectorcanreliablystoredata.Someharddiskcontrollersalsorecordpointersinthesectorheader,whichcandirectthedisktoareplacementsectorortrackwhentheoriginalsectoriswrong.Finally,thesectorheaderendswithacyclicredundancycheck(CRC)value,sothatthecontrollercancheckthereadoutofthesectorheadertoensureaccuracy.

Thedatasegmentofasectorisusedtostoredatainformation,includingdataanderrorcorrectioncodes(ECC)fordataprotection.Duringtheinitialpreparation,thecomputerfills512virtualinformationbytes(thestoragelocationoftheactualdata)andtheECCnumberscorrespondingtothesevirtualinformationbytesintothispart.

Princip přístupu

Zásobník

Zásobník je prostor pro zaznamenávání volací dráhy a parametrů, když je spuštěn program Jazyk: včetně rámce volání funkcí, předávání parametrů a ukládání zpáteční adresy a poskytuje proměnný prostor.

Basicknowledgeofstack

1.Související registry

1)esp:ukazatel horní části hromádky;

2)ebp:baseaddresspointer(ebpispoužitýkzaznamenáváníaktuálnífunkcevolázákladníadresuvClanguage);

3)cs:eippointsheaddressdalší instrukce,existují dva případy;

(1)Postupné provedení: vždy ukažte na další příkaz s po sobě jdoucími adresami;

(2)Skok/větvení:Po provedení tohoto návodu bude hodnota cs:eip upravena podle potřeb programu;

4)call:pusť aktuální hodnotuofcs:eipovrch zásobníku,cs:eippointdo vstupní adresy volanéfunkce;

5)ret:Pophodnotacs:eipůvodně zde uloženázvrchuzásobníkuavložce:eip;

6)iret:Popthecs:eip a vlajky původně uložené zde z horní části zásobníkuHodnota,putitincs:eipandflagregister.

2.Operace zásobníku

1)push:ukazatel navrchu zásobníku se zmenší o 4 bajty (32 bitů):

2)pop:ukazatel v horní části zásobníku se zvětší o 4 bajty (32 bitů).

Použití zásobníku během volání funkce

TheoperationofthestackduringthefunctioncallisshowninFigure3.AmainfunctioncallsaForsub-functions,thespecificstepsofthecallingprocessaredescribedasfollows:

  1. Před provedením hovoru esp ukažte navrchní část hromádky a debpbod na spodek sady;

  2. Po provedení volání se původní hodnota cs:eipis uloží do horní části zásobníku a poté se hodnota cs:eip zadá do vstupní adresy volaného programu;

  3. Zadejte volaný program,První instrukce:pushl%ebp,druháinstrukce:movl%esp,%ebp;

  4. Vstupte do volaného programu a pak může být zásobník vsunut do zásobníku atd. Normální provoz;

  5. Ukončete volaný program, první instrukce je rovna % ebp, % esp, druhá instrukce je rovná % ebp a třetí instrukce je obnovena. V tuto chvíli opusťte volaný program a obnovte hlavovou korunku na eip přes ret.

Princip lokality

Princip lokality se týká toho, k čemu je přístup, když CPU přistupuje k paměti, zda se jedná o pokyny nebo přístup k datům. Úložné jednotky jsou seskupeny v malé souvislé oblasti.

Lokalita obvykle má dva tvary:

Časová lokalita:Pokud není položka k informacím zpřístupněna, je pravděpodobné, že k ní bude v blízké budoucnosti znovu přístup.

Spatiallocality:Theinformationthatwillbeusedinthenearfutureislikelytobeclosetotheinformationcurrentlyinuseinthespatialaddress.

Alllevelsofmoderncomputersystems,fromhardwaretooperatingsystems,toapplications,aredesignedusingtheprincipleoflocality.Atthehardwarelevel,theprincipleoflocalityallowscomputerdesignerstosaverecentlyreferencedinstructionsanddataitemsbyintroducingasmallandfastcachememory,therebyincreasingthespeedofaccesstothemainmemory.Attheoperatingsystemlevel,thelocalityprincipleallowsthesystemtousemainmemoryasthemostrecentlyreferencedcacheinthevirtualaddressspace.Thelocalityprinciplealsoallowsthesystemtousethemainmemorytocachethemostrecentlyuseddiskblocksinthediskfilesystem.Theprincipleoflocalityalsoplaysanimportantroleinthedesignofanapplication.Forexample,aWebbrowserplacesarecentlyciteddocumentonalocaldisk,usingtemporallocality.AlargenumberofWebserversstorerecentlyrequesteddocumentsinfront-enddiskcaches.Thesecachescansatisfyuserrequestsforthesedocumentswithoutanyinterventionfromtheserver.

Thefollowingthreeexamplesareusedtoillustratethelocalityoftheprogram'sdatareference.

Příklad1:

intsumvec(intv[N])

{

inti=0,součet=0;

for(inti=0;i

{

součet+=v[i];

}

výnosový součet;

}

Intheabovecode,thevariablesumisreferencedonceineachloopiteration,whichhastimelocality.Fortheelementsofthearrayv,theyarestoredaccordingtothemTheorderinthememoryisreadsequentially,soithasspatiallocality,buteacharrayelementisonlyaccessedonce,soithasnotemporallocality.ItcanbeseenthatthesumvecfunctionhasbothspatiallocalityandtimefordataaccessLocality.

Příklad 2:

intsumarrayros(intv[M][N])

{

inti=0;j=0;součet=0;

for(i=0;i

for(j=0;j

{

součet+=v[i][j];

}

výnosový součet;

}

Intheabovecode,Theelementsofarrayvareaccessedaccordingtothestepsize1,soithasgoodspatiallocality(arrayelementsarestoredinroworder).

Příklad 3:

intsumarrayros(intv[M][N])

{

inti=0;j=0;součet=0;

for(j=0;j

for(i=0;i

{

součet+=v[i][j];

}

výnosový součet;

}

Intheabovecode,theelementsofthearrayvareaccessedaccordingtothestepsizeN,soitsspatiallocalityVerybad.Insummary,thefollowingconclusionscanbedrawn:

1)Programy, které opakovaně odkazují na stejnou proměnnou, mají dobrou časovou lokalitu;

2)ForthosewithasteplengthofkTheprograminthereferencemode,thesmallerthestepsize,thebetterthespatiallocality.Theprogramthatjumpsaroundinthememorywithlargesteps,thespatiallocalitywillbepoor;

3)Pro načítání instrukcíJinými slovy, smyčka má dobré tempo a prostorovou lokalitu. Čím menší těleso smyčky, tím více smyčky, tím lepší lokalita.

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