Virtual storage

Classification

Currently,thereisnounifiedstandardforthedevelopmentofvirtualstorage.Intermsofthetopologyofvirtualstorage,therearetwomainways:symmetricalandasymmetrical.Symmetricalvirtualstoragetechnologyreferstotheintegrationofvirtualstoragecontrolequipmentwithstoragesoftwaresystemsandswitchingequipmentasawhole,embeddedinthenetworkdatatransmissionpath;asymmetricvirtualstoragetechnologyreferstothevirtualstoragecontrolequipmentindependentofthedatatransmissionpathoutside.Intermsoftherealizationprincipleofvirtualizedstorage,therearealsotwoways;namely,datablockvirtualizationandvirtualfilesystem.Thedetailsareasfollows:

Symmetricalvirtualstorage

InthesymmetricalvirtualstoragestructureshowninFigure1,thestoragecontroldeviceHighSpeed​​TrafficDirectors(HSTD)andthestoragepoolsubsystemStoragePoolisintegratedtogethertoformSANAppliance.Itcanbeseenthatinthissolution,thestoragecontroldeviceHSTDplaysacentralroleintheprocessofdataexchangebetweenthehostandthestoragepool.Thevirtualstorageprocessofthisschemeisasfollows:thestoragemanagementsystemembeddedinHSTDvirtualizesthephysicalharddisksinthestoragepoolaslogicalstorageunits(LUNs),andperformsportmapping(specifywhichportsacertainLUNcanbeseenby),Thehostsidemapseachvisiblestorageunittoadriveletterthatcanberecognizedbytheoperatingsystem.WhenthehostwritesdatatotheSANAppliance,theuseronlyneedstospecifythedatawritelocationasthemappeddriveletter(LUN).ThedatapassesthroughtheHSTDhigh-speedparallelportandisfirstwrittentothecache.ThestoragemanagementsystemintheHSTDautomaticallyCompletetheconversionofthetargetlocationfromLUNtophysicalharddisk.Inthisprocess,theuserseesonlythevirtuallogicalunit,anddoesnotcareaboutthespecificphysicalorganizationofeachLUN.Theprogramhasthefollowingmainfeatures:

(1)Adoptalarge-capacityhigh-speedcache,whichsignificantlyimprovesthedatatransmissionspeed.

CacheisanintermediatemediumontheI/Opathbetweenthehostandthestoragedevice,whichiswidelyusedinstoragesystems.Whenthehostreadsdatafromthestoragedevice,itwillreadthedataconnectedtothecurrentdatastoragelocationintothecache,andkeepthedatathathasbeencalledmultipletimesinthecache;whenthehostreadsthedata,itislikelytobeabletoFindtherequireddatafromthecache.Readdirectlyfromthecache.Thespeedofreadingdatafromthecacheisonlyaffectedbythepropagationspeedoftheelectricalsignal(equaltothespeedoflight),soitismuchhigherthanthespeedofthedisk'smechanicalrotationwhenreadingdatafromtheharddisk.Whenthehostwritesdatatothestoragedevice,itfirstwritesthedataintothecache,waitsforthehostsidetostopthewriteaction,andthenwritesthedatafromthecachetotheharddisk,whichisalsohigherthanthespeedofdirectlywritingtotheharddisk

(2)Multi-portparalleltechnologyeliminatestheI/Obottleneck.

TraditionalFCstoragedeviceshaveafixedrelationshipbetweenthecontrolportandthelogicaldisk,andaccesstoaharddiskcanonlybedonethroughthecontrollerportthatcontrolsit.Inasymmetricalvirtualstoragedevice,therelationshipbetweenthestorageportoftheSANApplianceandtheLUNisvirtual,whichmeansthatmultiplehostscanconcurrentlyaccessthesameLUNthroughmultiplestorageports(upto8);inFibreChannel100MB/bandwidthUnderthepremisethatthemoreportsthatworkinparallel,thehigherthedatabandwidth.

(3)Logicalstorageunitprovideshigh-speeddiskaccessspeed.

Inthevideoapplicationenvironment,whentheapplicationprogramreadsandwritesdata,afixed-sizedatablock(from512byteto1MB)isusedastheunit.Inordertoensurethebandwidthrequirementsoftheapplication,thestoragesystemisoftendesignedtoachievethebestI/Operformancewhenthedatablocksizeisgreaterthan512byte.InthetraditionalSANstructure,whenthecapacitydemandincreases,theonlysolutionistobindmultipledisks(physicalorlogical)intoastripesettorealizealarge-capacityLUN.Inasymmetricalvirtualstoragesystem,thehostisprovidedwithtrulylarge-capacity,high-performanceLUNs,ratherthanlogicalvolumeswithpoorperformanceimplementedinastripedsetmethod.Comparedwithstripesets,PowerLUNshavemanyadvantages.Forexample,largeI/Oblockswillbetrulyacceptedbythestoragesystem,effectivelyincreasingthedatatransmissionspeed;andbecausethereisnostripesetprocessingprocess,thehostCPUcanrelievetheGreatburden,improvingtheperformanceofthehost.

(4)Thefault-tolerantperformanceofthepairedHSTDsystem.

Inasymmetricvirtualstoragesystem,HSTDistheplacewheredataI/Omustpass,andthestoragepoolistheplacewheredataisstored.Becausethedatainthestoragepoolhasafault-tolerantmechanismtoensuresafety,userswillnaturallythinkaboutwhetherHSTDhasfault-tolerantprotection.Likemanylarge-scalestoragesystems,inmaturesymmetricalvirtualstoragesystems,HSTDsareconfiguredinpairs,andeachpairofHSTDsarecacheddataconsistentandcommunicatewitheachotherthroughthenetworkmanagementserviceembeddedintheSANAppliance.

(5)OntheSANAppliance,theswitchingequipmentcanbeeasilyconnectedtorealizetheultra-large-scaleFabricstructureoftheSAN.

BecausethesystemmaintainsastandardSANstructure,whichprovidesatechnicalguaranteeforsystemexpansionandinterconnection,switchingequipmentcanbeeasilyconnectedtotheSANAppliancetorealizeasuper-large-scaleFabricstructureSAN.

Asymmetricalvirtualstoragesystem

IntheasymmetricalvirtualstoragesystemstructureshowninFigure2,eachhostinthenetworkisconnectedtoavirtualstoragemanagementdeviceTothediskarray,thedatapathofthehostreachesthediskarraythroughtheFCswitchingdevice;thevirtualstoragedevicevirtualizesthediskarrayconnectedonthenetwork,virtualizingtheLUNsineachstoragearrayasalogicalstripeset(Strip),andForeachhostonthenetwork,specifytheaccesspermissionsforeachStrip(writable,readable,andforbiddentoaccess).WhenthehostwantstoaccessaStrip,itmustfirstaccessthevirtualstoragedevice,readtheStripinformationandaccesspermissions,andthenaccessthedataintheactualStripthroughtheexchangedevice.Duringthisprocess,thehostwillonlyrecognizethelogicalstrip,butwillnotdirectlyrecognizethephysicalharddisk.Thissolutionhasthefollowingcharacteristics:

(1)Logicallycombinethecapacitiesofdifferentphysicalharddiskarraystorealizevirtualstripesets,andbindmultiplearraycontrollerportstoacertainextent.Increasetheavailablebandwidthofthesystem.

(2)Whenthenumberofswitchportsissufficient,twovirtualstoragedevicescanbeinstalledinanetworktorealizetheredundancyofStripinformationandaccessrights.

Butthisschemehassomeshortcomingsasfollows:

(1)Theschemeisessentiallyastripeset—diskarraystructure.OnceacertaindiskarraycontrollerisinthestripesetDamage,ordamagetothecoppercableorGBICinthepathfromthearraytotheswitch,willcauseavirtualLUNtogooffline,andthestripesetitselfisnotfault-tolerant.ThedamageofaLUNmeansthelossofdataintheentireStrip.

(2)Becausethebandwidthincreaseofthissolutionisachievedthrougharrayportbinding,andtheeffectivebandwidthoftheordinaryFibreChannelarraycontrollerisonlyabout40MB/S,itmustreachhundredsofmegabytes.Bandwidthmeanstocallmorethanadozenarrays,whichwilloccupydozensofswitchports.Thisisimpossibleinsmallandmedium-sizednetworkswithonlyoneortwoswitches.

(3)Sincetheperformanceofdiskarraysofvariousbrandsandmodelsisnotexactlythesame,ifthearraysofdifferentbrandsandmodelsareboundforthepurposeofvirtualization,aproblemwillarise:namelyWhendataiswrittenorread,thespeedofeachconcurrentdatastreamisdifferent,whichmeansthattheoriginaldatapacketsequenceisdisruptedafterthetransmissioniscompleted,andthesystemneedstimeandresourcestoreorderthedatapackets,whichwillseriouslyaffectSystemperformance.

Datablockvirtualizationandvirtualfilesystem

Theaboveanalysisanalyzesthesimilaritiesanddifferencesbetweensymmetricandasymmetricvirtualstoragesolutionsfromtheperspectiveoftopologicalstructure.ActuallyspeakingfromtheimplementationprincipleofvirtualizedstorageTherearealsotwoways;namely,datablockvirtualizationandvirtualfilesystem.

Thedatablockvirtualstoragesolutionfocusesonsolvingconflictsanddelaysduringdatatransmission.Inalarge-scaleFabricSANcomposedofmultipleswitches,sincemultiplehostsaccessstoragedevicesthroughmultipleswitchports,theproblemsofdelayanddatablockconflictsareveryserious.Thedatablockvirtualstoragesolutionusesvirtualmulti-portparalleltechnologytoprovideextremelyhighbandwidthformultipleclients,minimizingdelaysandconflicts.Inpracticalapplications,thedatablockvirtualstoragesolutionissymmetricalThetopologicalstructureisamanifestation.

Thevirtualfilesystemstoragesolutionfocusesonsolvingthesecuritymechanismoffilesharinginlarge-scalenetworks.Byassigningdifferentaccessrightstodifferentsites,thesecurityofnetworkfilesisguaranteed.Inpracticalapplications,thevirtualfilesystemstoragesolutiontakesanasymmetrictopologyasitsmanifestation.

Virtualstorage

Infact,itisakindoflogicalstorage,whichessentiallyprocessesphysicalstoragedeviceslogicallyandpresentsaunifiedlogicalviewtousers.Therefore,whenusersuseit,theyoperatevirtualdevicesanddonotneedtocareabouttheunderlyingphysicalenvironment.Therefore,thestoragespacebasedonheterogeneousplatformscanbefullyutilizedtoachieveoptimaluseefficiency.

Virtualstoragesystemfunction

Virtualstoragesystemgenerallyhasthefollowingfunctions:

(1)Ithasthefunctionofdeterminingthestoragedevicefailureandautomaticallytriggeringthereplacementofthefaileddevice.

(2)Withthefunctionoffreeconversionofstorageprotocols,itcansupportheterogeneousstorageandserverenvironmentsunderdifferentprotocols.

(3)SupportsSANstorageconfiguration,whichcanrealizecentralizedmanagementofstorageandstoragecapacityexpansion.

(4)ItcanrealizevariousremotesynchronizationoperationsofstorageonthenetworkthroughTCP/IPprotocol.

(5)Datacaching,scheduledautomaticbackupandrecovery,etc.canberealized.

Therefore,itsstorageefficiencyishighwheninuse,userstoragehardwareoverheadandmanagementandmaintenancecostscanbegreatlyreduced,systemsecurityisimproved,anditisespeciallysuitableforenterprise-levelandnetworkenvironmentswithmassiveinformationresourcesuse.

Characteristicanalysis

Wheneveryoumentionvirtualization,everyonewillthinkofsavingandgreenassoonaspossible.Becauseitsusecanreducecapitalinvestmentonequipmentandreducecostpressure.Foraperiodoftime,differentversionsoftheconceptofvirtualstorage(StorageVirtulization)haveemergedoneafteranother.Somehavebeeninterpretedfromasoftwareperspective,andsomehavebeenexemplifiedfromahardwareperspective.Eachmanufacturerhaspracticalproductsprovidedtousersbasedontheunderstandingofvirtualtechnology.Intermsofvirtualstorage,itisreallycontroversial,soitisdifficulttogiveaclearandaccuratedescriptionoftheconceptofvirtualstoragetechnology.

Nevertheless,summarizingthecommoncharacteristicsofsomevirtualstorage,itcanbeseenthattheso-calledvirtualstorageisthecentralizedmanagementofmultiplestoragemediamodules(suchasdisks,diskarrays)throughcertainmeans,andallstorageModulesaremanageduniformlyina"StoragePool".Inavirtualstorageenvironment,nomatterwhatthebackgroundphysicalstoragedeviceis,theserverandworkstationseethelogicalimageofthefamiliarstoragedevice.EvenifphysicalstorageoccursAfterchanges,thislogicalmirroringwillnotchange.Systemadministratorsdon’tneedtocareaboutbackgroundstorage,butonlyneedtofocusonmanagingstoragespace.Allstoragemanagementoperations,suchassystemupgrades,creationandallocationofvirtualdisks,changingRAIDlevels,andstorageexpansionSpaceismucheasierthanbefore,andstoragemanagementhasbecomeeasierandsimpler.

Fromtheuser’spointofview,asimplersentencecanbeusedtosummarizevirtualstorage-usestoragespaceinsteadofphysicalstorageHardware(disks,tapes),managestoragespaceinsteadofphysicalstoragehardware.

Virtualstoragetechnologyhasthefollowingcharacteristics:

1.Virtualstoragecangreatlyimprovestoragesystemperformance.Theoverallaccessbandwidthisalsooneofitsmostvaluablefeaturesforvideonetworksystems.Weknowthatthevideonetworkstoragesystemisgenerallycomposedofmultiplestoragemodules,andthevirtualstoragesystemcanperformloadbalancingwell.Thebandwidthrequiredforeachdataaccessisreasonablyallocatedtoeachstoragemodule,sothattheoverallaccessbandwidthofthesystemisincreased.Forexample,thereare4storagemodulesinastoragesystem,andtheaccessbandwidthofeachstoragemoduleis50MB/s,thetotalaccessbandwidthofthisstoragesystemcanbeclosetothesumofthebandwidthofeachstoragemodule,whichis200MB/s.

2.Virtualstoragetechnologyprovidesacentralizedmanagementmethodforalarge-capacitystoragesystem.Onelinkinthenetwork(suchasaserver)ismanagedinaunifiedmannertoavoidmanagementtroublescausedbytheexpansionofstoragedevices.Forexample,whenageneralstoragesystemisused,whenanewstoragedeviceisadded,theentiresystem(includingnetworkManyuserequipmentsinthestoragesystemneedtobere-configuredsothatthis"newmember"canbeaddedtothestoragesystem.Withvirtualstoragetechnology,whenaddinganewstoragedevice,onlythenetworkadministratorneedstoThestoragesystemperformsrelativelysimplesystemconfigurationchanges,andtheclientdoesnotneedanyoperation,butonlyfeelsthatthecapacityofthestoragesystemhasincreased.

3.Virtualstoragetechnologyprovidesbetterflexibilityforstorageresourcemanagement.Itcancentrallymanageandusedifferenttypesofstoragedevices,whichguaranteestheuser'spreviousinvestmentinpurchasingstoragedevices.

Implementationmethods

Currently,virtualstorageismainlydividedintothefollowingtypes:

Virtualstorageontheserverside

Servervendorswillimplementvirtualstorageontheserverside.Similarly,softwarevendorswillalsoimplementvirtualstorageontheserverplatform.ThisTheimplementationofthesevirtualstorageistomaptheimagetotheperipheralstoragedevicethroughtheserverside,exceptforthedistributionofdata,thereisnocontrolovertheperipheralstoragedevice.Theserversidegenerallyimplementsvirtualstoragetechnologythroughlogicalvolumemanagement.Logicalvolumemanagementprovidesavirtuallayerformappingfromphysicalstoragetologicalvolumes.Theserveronlyneedstodealwithlogicalvolumeswithoutmanagingthephysicalparametersofstoragedevices.

Withthiskindofvirtualstoragesystem,theserversideisaperformancebottleneck,soitisrarelyusedinthefieldofmultimediaprocessing.

Virtualstorageonthestoragesubsystemside

Anotherplacetoimplementvirtualizationisthestoragedeviceitself.Thiskindofvirtualstorageisgenerallyimplementedbystoragevendors,butitislikelytousevendor-onlystorageproducts.Toavoidthisincompatibility,vendorsmaycooperatewithserver,software,ornetworkvendors.Whenvirtualstorageisimplementedonthedeviceside,thelogical(virtual)environmentandthephysicaldeviceareinthesamecontrolrange.Thebenefitsofthisare:virtualdisksusediskcapacityhighlyefficiently,andvirtualtapesusetapemediahighlyefficiently.

Thevirtualstoragedeviceonthestoragesubsystemismainlyconnectedtotheserverthroughalarge-scaleRAIDsubsystemandmultipleI/Ochannels.TheintelligentcontrollerprovidesLUNaccesscontrol,caching,andotherdatareplication,etc.Managementfunctions.Theadvantageofthismethodisthatthestoragedeviceadministratorhascompletecontroloverthedevice,andbyseparatingitfromtheserversystem,thestoragemanagementcanbeisolatedfrommultipleserveroperatingsystems,andthehardwareparameterscanbeeasilyadjusted.

Implementvirtualstorageonthenetworkdeviceside

Networkmanufacturerswillimplementvirtualstorageonthenetworkdeviceside,andmaplogicalimagestoperipheralstoragedevicesthroughthenetwork.Inadditiontoallocatingdata,theperipheralstorageThedevicedoesnothaveanycontrol.Theimplementationofvirtualstorageonthenetworksideisreasonable,becauseitsimplementationisneitherontheserverside,noronthestoragedeviceside,butbetweenthetwoenvironments.Itmaybethemost"open"virtualimplementationenvironment.Itispossibletosupportanyserver,operatingsystem,applicationandstoragedevice.Technicallyspeaking,therearetwotypesofstructuresforimplementingvirtualstorageonthenetworkside:symmetricalandasymmetricalvirtualstorage.

Fromtheactualsituationofcurrentvirtualstoragetechnologyandproducts,host-basedandstorage-basedmethodsarethemostattractiveforearlyadopters,becausetheydonotneedanyadditionalhardware,butforheterogeneousAsfarasthestoragesystemandoperatingsystemareconcerned,theperformanceofthesystemisnotverygood.Themethodbasedoninterconnecteddevicesissomewherebetweenthetwo.Itavoidssomesecurityissues,hasastrongstoragevirtualizationfunction,canreducetheloadofasinglehost,andcanobtaingoodscalability.

Nomatterwhatkindofvirtualstoragetechnologyisadopted,itspurposeistoprovideahigh-performance,safe,stable,reliable,andexpandablestoragenetworkplatformtomeetthedemandingrequirementsoftheprogramproductionnetworksystem.Accordingtothecomprehensiveperformance-priceratio,undernormalcircumstances,virtualstoragetechnologybasedonhostandstoragedevicecanguaranteethedataprocessingcapacityofthesystem,itisgivenpriority,becausethesetwovirtualstoragetechnologiesareconvenientinstructure,simpleinmanagement,andeasytomanage.Themaintenanceiseasy,theproductisrelativelymature,andtheperformance-priceratioishigh.Inthecasethatpurestoragedevice-basedvirtualstoragetechnologycannotguaranteetheperformancerequirementsofthestoragesystem,wecanconsideradoptingvirtualstoragetechnologybasedoninterconnecteddevices.

Features

Virtualstoragehasthefollowingcharacteristics:

(1)Virtualstorageprovidesameansforcentralizedmanagementofalarge-capacitystoragesystem.Links(suchasservers)aremanagedinaunifiedmanner,avoidingmanagementtroublescausedbystoragedeviceexpansion.Forexample,whenusingageneralstoragesystem,whenanewstoragedeviceisadded,theentiresystem(includingmanyuserdevicesinthenetwork)needstobereconfiguredwithtediousconfigurationworkbeforethis"newmember"canbeaddedtothestoragesystem.Withvirtualstoragetechnology,whenaddingnewstoragedevices,onlythenetworkadministratorisrequiredtomakerelativelysimplesystemconfigurationchangestothestoragesystem.Theclientdoesnotneedanyoperations,anditfeelslikethecapacityofthestoragesystemisonlyincreased.

(2)Themostvaluablefeatureofvirtualstorageforvideonetworksystemsisthatitcangreatlyincreasetheoverallaccessbandwidthofthestoragesystem.Thestoragesystemiscomposedofmultiplestoragemodules,andthevirtualstoragesystemcanperformloadbalancingwell,andreasonablyallocatethebandwidthrequiredforeachdataaccesstoeachstoragemodule,sothattheoverallaccessbandwidthofthesystemisincreased.Forexample,ifthereare4storagemodulesinastoragesystem,andtheaccessbandwidthofeachstoragemoduleis50MBps,thetotalaccessbandwidthofthisstoragesystemcanbeclosetothesumofthebandwidthsofthestoragemodules,thatis,200MBps.

(3)Virtualstoragetechnologyprovidesbetterflexibilityforstorageresourcemanagement.Differenttypesofstoragedevicescanbecentrallymanagedandused,whichguaranteestheinvestmentofstoragedevicespurchasedbyusersinthepast.

(4)Virtualstoragetechnologycanprovidesomeotherusefulfunctionsforthenetworksystemthroughmanagementsoftware,suchasremotemirroringwithoutaserver,snapshotsofdata,etc.

Application

Duetotheabove-mentionedcharacteristicsofvirtualstorage,virtualstoragetechnologyisgraduallybecomingthemainstreamtechnologyofsharedstoragemanagement.Itsapplicationisasfollows:

Datamirroring

Datamirroringistocreatedatacopiesbetweendifferentstoragedevicesthroughtwo-waysynchronizationorone-waysynchronizationmode.Areasonablesolutionshouldbeabletoprovideamethodformirroringbetweenthesamestoragearrayanddifferentstoragearrayswithoutrelyingontheequipmentmanufacturerandoperatingsystemsupport.

Datareplication

Long-distancedatamigration(usuallyasynchronoustransmission)viaIPaddressisanextremelyimportantdatadisasterrecoverytoolforenterprisesofdifferentsizes.Agoodsolutionshouldnotrelyonspecialnetworkequipmentsupport,andatthesametime,itshouldnotrelyonthehosttosavethemanagementcostoftheenterprise.

Tapebackupenhancementdevice

Inthepastfewyears,therehavebeenfewnewdevelopmentsintapebackuptechnology.Nevertheless,anetworkstoragedeviceplatformshouldalsobeabletobuildabridgebetweentapesanddiskstocompletethebackupworkathighspeed,smoothlyandsafely.

Real-timecopy

Fortesting,expansionandaggregationorsomeotherreasons,companiesoftenneedtomakedatacopies.

Real-timedatarecovery

Usingtapetorestoredataisthemainmethodofdatarecovery,butitisoftendifficulttosucceed.Oneoftheimportantnewdevelopmentdirectionsofdatamanagementistotransferthebackupdatainthenearterm(whichcanbehistoricaldataseveralweeksago)todiskmediainsteadoftapemedia.Recoveringdatafromdiskisasfastaslightning(allfilescanberecoveredin60seconds),anditisfarsaferandmorereliablethanrecoveringdatafromtape.Atthesametime,theentirevolume(Volume)datacanberestored.

Applicationintegration

Anothernewdirectioninthedevelopmentofstoragemanagementistobringservicesclosertoapplications.Nomanagerinthefieldofinformationtechnologywillbuyitoutofpureinterestinstoragedevices.Storagedevicesareusedtoserveapplications,suchasdatabases,communicationsystems,andsoon.Byintegratingstoragedeviceswithkeyenterpriseapplicationbehaviors,greatervaluecanbeobtained,andatthesametime,thedifficultiesencounteredintheoperationprocesscanbegreatlyreduced.

Applicationofvirtualstorageindigitalvideonetwork

NowIwillfocusontheapplicationofvirtualstorageindigitalvideonetwork.

Digitalvideonetworkisnolongeranunfamiliarconcepttotheradioandtelevisionindustry.Becauseitplaysanimportantroleinthedigitalizationofradioandtelevisiontechnology,domestictelevisionstationsatalllevelspaygreatattentiontoit.,Andbegantoconstructandapplythistypeofsystem.Intheconceptofdigitalvideonetwork,thetraditionalstructureofavideorecorder,aneditingsystem,andabroadcastingsystemwascompletelybroken,andtheuploadingworkstationandeditingproductionworkstationwerereplaced.,Theflowofthebroadcastworkstationandtheprogramstorageworkstationiseasytooperateandmanage.Programuploading,programediting,andprogrambroadcastingarecompletedonworkstationswithdifferentfunctions,whichcandoubletheworkefficiency.Atthesametime,duetothenon-lineareditingsystem,inadditiontothecompressionlossduringacquisition.Therewillbenomorelossintheproductionandbroadcastingofthesignal,andthetechnicalqualityoftheprogramwillbegreatlyimproved.

Intheexistingvideonetworksystem,althoughthemainfrequencyofthecomputer,thetransmissionrateofthenetworkandtheperformanceoftheswitchingdevicecanalreadymeettherequirementsofmostapplications,theaccessbandwidthofthestoragedeviceisproblematic.Becomeamajorperformancebottleneckofthesystem.Videoeditingandproductionhavethecharacteristicsoflargedatastorage,highcodestream,strongreal-timeperformance,andimportantsecurity.Thisrequiresstoragetechnologiesandproductsusedinthevideofieldtohavesufficientbandwidthandgoodstability.

Inastand-aloneapplication,inordertoensurethataneditingsitehasenoughdatabandwidth,SCSItechnology,localindependentdiskredundantarrayRAID(RedundantArrayofIndependentDisks)technology(includingsoftwareandhardware)isWidelyused,itcombinesseveralSCSIharddisksandcontrollerstoformalarge-capacity,fast-response,andhighlyreliablestoragesubsystem,whichcanbeusedasalogicaldiskorvirtualdiskfromtheuser’spointofview,thusgreatlyimprovingthedatatransferrateandStoragecapacity,whileusingerrorcorrectiontechnologytoimprovestoragereliabilityandmeetbandwidthrequirements.

Withthedevelopmentofprogramproductionrequirements,2-3stationsarerequiredtoshareeditingdata.Atthistime,SCSInetworktechnologycanbeusedtoachievethisrequirement.Severaleditingsitesareequippedwithhigh-performanceSCSIadapters,connectedtoasharedSCSIdiskarray,whichcannotonlyrealizethesharingofdataamongseveralsites,butalsoensuretheworkingbandwidthofeachsinglemachine.

ThematureapplicationofFibreChanneltechnologyisamilestoneinthedevelopmentofvideonetworks.Sincethen,theconnectiondistancebetweenthehostandthesharedstoragedevicehasbeenlimitedfromafewmetersortenmeterstoseveralhundredmetersorseveralkilometers.,Andcombinedwithfiberchannelswitchingequipment,thenetworkscalehasbeenexpandedseveraltimesormorethantentimes.Atthistime,theFC(FibreChannel)diskarray-RAIDfault-toleranttechnology,relativelyhighbandwidthandlargecapacityofSCSI,hasbecomethecorestoragedeviceinthevideonetwork.

WiththedevelopmentofTVstations,theapplicationoflarge-scalevideonetworksattheentirestationlevelhasbeenproposed.Underthisdemand,moreadvancedstoragetechnologiesandproductsmustbeintroducedintothevideofield.Thedevelopmentofstorageareanetwork(SAN)iscurrentlyinaperiodoffull-speedrise,andvariousconceptsareemergingoneafteranother.Oneofepoch-makingsignificanceistheconceptofvirtualstorage.ComparedwiththetraditionalswitchandRAIDarray,thehostdirectlyaccessestheSANstructureoftheharddiskinthearraythroughthehardwarelayer.Thepositioningofvirtualstorageistoabstractthedatastoragefunctionfromtheactualandphysicaldataaccessprocess,sothatordinaryuserscanWhenaccessingdata,thereisnoneedtocareabouttheconfigurationparameters,physicallocationandcapacityofthespecificstoragedevice,therebysimplifyingtheworkdifficultyforusersandsystemadministrators.

Whendesigningavideonetworksystem,thefollowingfactorsshouldbeconsideredfortheselectionofthestoragesystem:(1)overallbandwidthperformance;(2)manageability;(3)security;(4)Scalability;(5)Systemcost.

Ofcourse,thesefactorssometimesrestricteachother,especiallytherelationshipbetweensystemcostandperformanceandsafety.Howtofindareasonable,practicalandeconomicalcooperationbetweenthesefactorsisaproblemthatneedstobesolved.Theemergenceofvirtualstoragetechnologyprovidesuswithafeasiblehigh-performanceandcost-effectivesolutionwhenbuildingvideonetworksystems.

Fromthetopologicalstructure,thesymmetricalsolutionhashigherbandwidthperformanceandbettersecurityfeatures,soitismoresuitableforlarge-scalevideonetworkapplications.Theasymmetricsolutionadoptsthevirtualfileprinciple,soitismoresuitablefortheapplicationofordinarylocalareanetwork(suchasofficenetwork).