信息存储材料与技术

信息存储材料与技术第一页，共二十九页，2022年，8月28日第二页，共二十九页，2022年，8月28日光存储光存储最早的形式是缩微照相：文档资料长期保存的主要形式。将文献摄影，存放于缩微胶片上，缩微胶卷、缩微教胶片、缩微卡片等。激光全息：实现三维图像存储不能进行实时数据存取。光盘技术：光盘存储技术是本世纪70年代开拓出来的。光盘存储集成系统中，光盘机和光盘片是核心器件。在光盘机中光学读、写头是关键元件。第三页，共二十九页，2022年，8月28日

光盘存储器（简称“光盘”）是利用激光原理存储和读取信息的媒介。光盘片用塑料制成，塑料中间夹入了一层薄而平整的铝膜，通过铝膜上极细微的凹坑记录信息。只读光盘：信息是光盘制作时在盘面上一次性形成的，只能读出

使用，不能重新写入。工厂通过压制方法生产光盘时，将信息以凹坑形式生成在铝膜上，成为永久的信息记录。一片普通5”只读光盘可以存放650MB的信息。只读光盘是一种非常好的可以长期保存的存储介质，今天许多商品软件和信息资料都被制成光盘销售。刻录光盘：数据一旦进入光盘，所占的空间是不能释放的。可读写光盘：也已投放市场。光盘的结构特点和工作原理第四页，共二十九页，2022年，8月28日光盘和工作原理光盘表面：0/1光盘外观光盘工作原理激光束撞击光盘表面凹坑平面棱镜反射激光束激光二极管感光二极管聚焦光脉冲转换为0/1第五页，共二十九页，2022年，8月28日偶氮第六页，共二十九页，2022年，8月28日光存储基本原理光烧孔：光物理烧孔、光化学烧孔第七页，共二十九页，2022年，8月28日电子俘获第八页，共二十九页，2022年，8月28日第九页，共二十九页，2022年，8月28日第十页，共二十九页，2022年，8月28日Itisestimatedthatthehumanracehascreatedabout1exabyte(1018)ofinformationtodate.Itisalsopredictedthatthenextexabytecouldbegeneratedwithinthenextthreeyears.Thisunprecedentedgrowthininformationposesanumberofsignificantchallengesintermsofinformationstorage,transmission,networking,andaccess.Storageservicesarecurrentlygrowingat120percentaYearandaredirectlylinkedtothegrowthingeographicallygeographicallydispersedonlineactivities.

第十一页，共二十九页，2022年，8月28日Organizationsarerapidlyrealizingthattheircentraldatastoragefacilitiesarecalledonbyemployeesnotonlyinthemetropolitanarea,butworldwide.Opticalnetworks,however,havenotbeendevelopedandoptimizedwithdatastorageinmind,althoughitisnowrealizedthattheyrepresentthemainsolutionavailabletodayfornetworkinggeographicallydispersedstorageandusers.第十二页，共二十九页，2022年，8月28日Fabricattachedstorage,whichincludesstorageareanetworks(SANs)andnetworkattachedstorage(NAS),representsoneofthefastestgrowingareasofnetworking.Itsgoalsincludeprovidingtimelyaccesstoinformation,largecapacity,dynamicreconfigurablebehavior,dataprotectionandrestoration,aswellascoveringalargeGeographiccoverage.SANscanofferuniqueadvantages,includingconsolidatedstoragewithcostsavingsandreconfigurability,greaterutilityofcentralized/distributeddata,anddataprotectionthroughreplicationfordisasterrecovery.Thisfeaturetopicprovidesanoverviewofopticalstorageareanetworks.第十三页，共二十九页，2022年，8月28日considersnext-generationopticalstorageareanetworksbasedonthelight-trailsapproachtodynamicwavelengthprovisioning.ItdiscussesSANextensionsbasedonlight-trailsandpaysattentiontoDisasterrecoveryandgridcomputinginthecontextofSANs.evaluatesthereliabilityandavailabilityofSANextensionsolutionsincludingIPbasedextensionsandFibreChannel(FC)-basedextensions.considersdispersioncompensationforSANswheredatacentersstilluselegacy第十四页，共二十九页，2022年，8月28日multimodefiberwithalimitedbandwidth-distanceproduct.ThearticlediscussestheuseofenhancedBandwidthmultimodefiber,electronicdispersioncompensation,andtheuseofwavelengthtuningcontrolloops.addressesreconfigurablefree-spaceopticalswitchesforSANs.Itintroducesaholographicbeamsteeringopticalswitchandshutter-basedopticalswitches,andpaysattentiontoopticalpacketswitchingforSANs.Itishopedthatthisfeaturetopicpresentsabalancedviewofdevelopmentsinindustryandacademiainthisrapidlydevelopingfield.第十五页，共二十九页，2022年，8月28日ThevastexplosionofdatatrafficandthegrowingdependenceofthefinancialworldonelectronicserviceshaveledtoatremendousincentiveforSANservicesandstorage-capablenetworks.CoupledwithaneedtostoreinformationandDynamicallyreproduceitinrealtime,SANsareexperiencinganewupwardthrust.LocalSANsbasedontheintra-officeclient-serverhub-and-spokemodelhavelongbeendeployedasthedefactostandardforbackingupserversandhigh-endcomputingdeviceswithincampusesandpremises.Next-GenerationOpticalStorageAreaNetworks:TheLight-TrailsApproach第十六页，共二十九页，2022年，8月28日withthegrowthoftheInternet,backofficeoperations,andaneedforsecurebackupatgeographicallydiverselocations,SANshavemovedfromtheirpremisesconfinementtoalargerareaofproliferation.ThesenewcategoriesofSANsites,alsoknownasInternetdatacenters(IDCs),arebecomingincreasinglyImportantfromtherevenueaswellassecurityperspectives.Thesesitesareconnectedtooneanotherandtotheirclientnodesthroughatransportmedium.第十七页，共二十九页，2022年，8月28日Consideringthehighvolumeofdatathatistransferredbetweenclientsandserverstoday,transportislikelytotakeplaceacrossopticalcommunicationlinks.Opticalfiberofferslargebandwidthforhigh-volumetransferwithgoodreliabilitytofacilitatesynchronousbackupcapabilitiesbetweenSANsitesandclientsorbetweenmultipleSANsitesinservermirroringoperations.Currently,opticalchannelsareusedonlyfortransportofinformation,whilestandardizedprotocolssuchasFibreChannel,ESCON,andFICONoperateatthedatalayer,enablingactualtransferofinformation.第十八页，共二十九页，2022年，8月28日Withthesharpriseintheneedfordynamicservices,futureSANsystemsshouldbeabletocatertodynamicprovisioningof“connections”betweenserversitesandclients.Bandwidthprovisioninginalow-costsetupisthekeychallengeforfutureSANsystems.ThemostnaturalwaytofacilitatetheseservicesistoenableaprotocolResidinghierarchicallyoverthedatalayers,facilitatingthenecessarydynamisminbandwidtharbitrationaswellasguaranteeingqualityofservice(QoS)attheopticallayer.第十九页，共二十九页，2022年，8月28日This,however,complicatestheprocessandleadstoexpensivesolutionsasnodesthenwouldhavetoperformhierarchicalprotocoldissemination.Theopticallayerthathassofarbeenusedprimarilyjustfortransportcan,however,bepushedfurthertosatisfysomeofthecutting-edgeneedsofnext-generationSANsystems.Theseincludemulticastingformultisitemirroring,dynamicprovisioningforlow-costasynchronousbytimelybackup,andprovidingalow-costsystemthattakesadvantageofthereliabilityandresiliencyoftheOpticallayer.第二十页，共二十九页，2022年，8月28日Figure1.Theconceptualdifferencesbetweenalightpathandalight-trail,andthearchitectureofalight-trailnode.Thefirstnodeistheconvenernode,thelastnodeistheendnode.Thelight-trial,whichessentiallyresidesonawavelength,isopticallyswitchedbetweenthesetwonodes.Multiplelight-trailscanusethesamewavelengthaslongasthewavelengthsdonotoverlap,therebyleadingtospatialreuseofthewavelength.Light-trailspresentasuitablesolutionfortrafficgrooming.Multiplenodescanshareanopenedwavelengthinanoptimumwaytomaximizethewavelength’sutilization.第二十一页，共二十九页，2022年，8月28日Alight-trailisageneralizationofalightpath(opticalcircuit)inwhichdatacanbeinsertedorremovedatanynodealongthepath.Light-trailsareagroupoflinearlyconnectednodesCapableofachievingdynamicprovisioninginanopticalpaththroughanout-of-bandcontrolchannel(overlaidprotocol).Thisleadstomultiplesource-destinationpairsabletoestablishtimedifferentiatedconnectionsoverthepathwhileeliminatingtheneedforhigh-speedswitching.

第二十二页，共二十九页，2022年，8月28日Alight-trailischaracterizedbyasegmentofnodesthatfacilitateunidirectionalcommunication.Anodeinalight-trailemploysthedrop-and-continuefeature,whichallowsnodestoCommunicatetooneanotherthroughnon-time-overlappingconnectionswithoutopticalswitching.Theswitchlessaspectmakesalight-trailanalogoustoanopticalbus.However,alight-trail,duetoitsout-of-bandprotocol,enhancestheknownpropertiesofanopticalbus.第二十三页，共二十九页，2022年，8月28日第二十四页，共二十九页，2022年，8月28日Considerann-nodelight-trailA1,…,An

asshowninFig.2.assumethateachnodeisconnectedtoaSANinterfacelikeFibreChannel.assumethatkofthesennodesareclientnodes(sources),andtheremainingn–knodesareservers(primarilysinks)thatstorethedatasomewhatinrealtime(synchronously).DatathatarrivesatthekSANclientinterfacesfromtheirclientnetworkisbufferedintheFibreChannelinterfacebuffersthataretypically8–256Mb,andareusedtostorethedatauntilan