《信息科学类专业英语》课件第5章

Lesson5IntroductiontoCloudComputing(第五课云计算简介)

Vocabulary(词汇)ImportantSentences(重点句)QuestionsandAnswers(问答)Problems(问题)ReadingMaterial(阅读材料)

NumeroussurveysreportthatCloudComputingwillbeatop10technologythatenterprisebusinessmanagersneedtobeawareoffor2010.Notthatyoucanescapethemarketingandinformationpublishedaboutthislatestsuperhypedtopic.MuchofthemessagefocusesonCloudComputingasalowercostdeliverymodelforITservices.Thismayormaynotbetrue.1SoWhatisCloudComputing?

WeseeCloudComputingasacomputingmodel,notatechnology.Inthismodel“customers”plugintothe“cloud”toaccessITresourceswhicharepricedandprovided“on-demand”.Essentially,ITresourcesarerentedandsharedamongmultipletenantsmuchasofficespace,apartments,orstoragespacesareusedbytenants.DeliveredoveranInternetconnection,the“cloud”replacesthecompanydatacenterorserverprovidingthesameservice.Thus,CloudComputingissimplyITservicessoldanddeliveredovertheInternet.RefertosectionofTypesofCloudComputing.

CloudComputingvendorscombinevirtualization(onecomputerhostingseveral“virtual”servers),automatedprovisioning(servershavesoftwareinstalledautomatically),andInternetconnectivitytechnologiestoprovidetheservice.[1]Thesearenotnewtechnologiesbutanewnameappliedtoacollectionofolder(albeitupdated)technologiesthatarepackaged,soldanddeliveredinanewway.

Akeypointtorememberisthat,atthemostbasiclevel,yourdataresidesonsomeoneelse’sserver(s).Thismeansthatmostconcerns(andtherearepotentiallyhundreds)reallycomedowntotrustandcontrolissues.Doyoutrustthemwithyourdata?2TheEconomics

EconomiesofscaleandskilldriveCloudComputingeconomics.AswithrentedRealEstate,thecostsofownershiparepooledandspreadamongalltenantsofthemulti-tenantCloudComputingsolution.Consequentially,acquisitioncostsarelowbuttenantsneverownthetechnologyassetandmightfacechallengesiftheyneedto“move”orendtheserviceforanyreason.[2]

SomethingthatisoftenoverlookedwhenevaluatingCloudComputingcostsisthecontinuedneedtoprovideLANservicesthatarerobustenoughtosupporttheCloudsolution.Thesecostsarenotalwayssmall.Forexample,ifyouhave6ormoreworkstationcomputers,youwillprobablyneedtocontinuetomaintainaserverinadomaincontrollerrole(toensurenameresolution),atleastoneswitch(toconnectallofthecomputerstoeachotherandtherouter),oneormorenetworkedprinters,andtherouterfortheInternetconnection.3WhatdoIneedtouseCloudComputing?

AllthatisreallyneededtoacquireanduseCloudComputingsolutionsisacreditcard(orotherpaymentmethod)andaLANwithanInternetconnectionrobustenoughtosupporttheClouddeliveredservice.Thesetworequirementsaredeceptivelysimple.

Fromatechnicalpointofviewthebiggestchallengeforbusinesses,particularlySMBs,maybetheneedforanappropriatelyrobustLANinfrastructureandInternetconnection.Typically,InternetaccessisprovidedbyasinglecommercialserviceISPproviderthroughasingleportonarouter.AcharacteristicofthistypeinstallationisthatallofthecomputersconnectingthroughtheLANsharetheInternetbandwidthequally.Thiscanquicklybecomeanissue.

Forexample:VerizonFiOSInternet15/2(down/up)servicemighthaveameasuredspeedof14420/1867Kbps.Thiswouldseemtobeplentyofspeed.However,supposeabusinesshad5computersusingaCloudsolutionandsendingdatatothecloudforprocessing.Thebandwidthavailabletoeachcomputerwouldbe373Kbps(up1867/5).Thatisabout46(8bit)characterspersecondtothecloudapplicationanddoesnotincludeanycommunicationorapplicationdata.Thecloudsolutionmightnotworkorresponsessoslowastobeunacceptable.Itisn’tthedownloadspeedthatbecomesalimit,butheuploadspeed.RefertoPage5foraBandwidthChart.

Theon-demandnatureofCloudComputingpresentsadilemma:Theon-demandmodelincludesaself-serviceinterfacethatallowsuserstoself-provisionservices(forexamplestorage).[3]Thisempowersusersbutcanmakeservicestooeasytoacquireandconsume.ToquoteanITadministrator“Peoplecouldcarelessaboutpolicies.Theywantwhattheywantwhentheywantit.Theydon’tinvolveIT.”

ConsiderthefacultymemberattheUniversityofMassachusettswhoquietly(withoutanyone’sknowledge)usedacloudservicetobackup20GBofdataeachnightovertheInternetbringingtheschoolLANtoitsknees.HowmanagementcontrolsCloudComputingisuniquetoeachorganizationandisanITGovernanceissue.4Conclusion

Weareoftentoldparticularlybyvendorsandevangelists,“Youdon’tlikeOutsourcedorCloudComputingsolutions”.Thisissimplynottrue.Outsourcingandusingthirdpartiesforservicecanbeveryhelpfultoclients.However,wedonotthinkthatthesesolutionsareappropriateoreffectiveineverysituationorforeveryorganization.5TypesofCloudComputing

5.1SaaS(SoftwareasaService)

Isthemostwidelyknownandwidelyusedformofcloudcomputing.Itprovidesallthefunctionsofasophisticatedtraditionalapplicationtomanycustomersandoftenthousandsofusers,butthroughaWebbrowser,nota“locally-installed”application.[4]LittleornocodeisrunningontheUserslocalcomputerandtheapplicationsareusuallytailoredtofulfillspecificfunctions.SaaSeliminatescustomerworriesaboutapplicationservers,storage,applicationdevelopmentandrelated,commonconcernsofIT.

Highest-profileexamplesareS,Google’sGmailandApps,instantmessagingfromAOL,YahooandGoogle,andVoIPfromVonageandSkype.

5.2PaaS(PlatformasaService)

Deliversvirtualizedserversonwhichcustomerscanrunexistingapplicationsordevelopnewoneswithouthavingtoworryaboutmaintainingtheoperatingsystems,serverhardware,loadbalancingorcomputingcapacity.ThesevendorsprovideAPIsordevelopmentplatformstocreateandrunapplicationsinthecloud(e.g.usingtheInternet).ManagedServiceproviderswithapplicationservicesprovidedtoITdepartmentstomonitorsystemsanddownstreamapplicationssuchasvirusscanningfore-mailarefrequentlyincludedinthiscategory.[5]

WellknownproviderswouldincludeMicrosoft’sAzure,Salesforce’sF,GoogleMaps,ADPPayrollprocessing,andUSPostalServiceofferings.

5.3IaaS(InfrastructureasaService)

Deliversutilitycomputingcapability,typicallyasrawvirtualservers,ondemandthatcustomersconfigureandmanage.HereCloudComputingprovidesgridsorclustersorvirtualizedservers,networks,storageandsystemssoftware,usually(butnotalways)inamultitenantarchitecture.IaaSisdesignedtoaugmentorreplacethefunctionsofanentiredatacenter.Thissavescost(timeandexpense)ofcapitalequipmentdeploymentbutdoesnotreducecostofconfiguration,integrationormanagementandthesetasksmustbeperformedremotely.

VendorswouldincludeA(ElasticComputeCloud[EC2]andSimpleStorage),IBMandothertraditionalITvendors.

1．hypevt.使增加;夸大;<俚>(用刺激针剂等)强行刺激,使兴奋(up)。

2．on-demand在要求时,一经请求;在要求支付时。

3．essentiallyadv.本质上,本来,根本。

4．provisionn.供应,(一批)供应品,预备,防备,规定。

5．potentiallyadv.潜在地。Vocabulary

6．infrastructuren.基础;基础结构[设施](尤指社会、国家赖以生存和发展的)；【建】基[底]层结构,下部结构；【军】永久性防御设施,永久性基地。

7．dilemman.进退两难的局面,困难的选择。

8．empowervt.授权,准许;使能够。

9．outsourcing[商]外部采办,外购。

10．sophisticatedadj.诡辩的,久经世故的。

11．downstreamadv.下游地adj.下游的n.后台处理程序。

12．multitenantn.多承租；多租户。

[1]CloudComputingvendorscombinevirtualization(onecomputerhostingseveral“virtual”servers),automatedprovisioning(servershavesoftwareinstalledautomatically),andInternetconnectivitytechnologiestoprovidetheservice.

云计算提供商将虚拟化(一台计算机主机对应多个虚拟服务器)、自动运行维护(服务器具有自动安装的软件)以及因特网连接技术组合来提供这些服务。ImportantSentences

[2]Consequentially,acquisitioncostsarelowbuttenantsneverownthetechnologyassetandmightfacechallengesiftheyneedto“move”orendtheserviceforanyreason.

必然地，买进成本是低的，但是承租人从未拥有技术财产，并且如果他们因任何原因需要转移或结束这项服务时可能面临挑战。

[3]Theon-demandnatureofCloudComputingpresentsadilemma:Theon-demandmodelincludesaself-serviceinterfacethatallowsuserstoself-provisionservices(forexamplestorage).

云计算的按请求服务的本质呈现这样一种尴尬：按请求服务的模型包含一种自服务的接口以允许用户使用一些自规定的服务(如存储)。

[4]Itprovidesallthefunctionsofasophisticatedtraditionalapplicationtomanycustomersandoftenthousandsofusers,butthroughaWebbrowser,nota“locally-installed”application.

它通过网络浏览器，而不是本地安装的应用程序，提供所有的复杂的传统应用功能给许多客户，通常有数以千计的用户。

[5]ManagedServiceproviderswithapplicationservicesprovidedtoITdepartmentstomonitorsystemsanddownstreamapplicationssuchasvirusscanningfore-mailarefrequentlyincludedinthiscategory.

管理服务提供商将应用服务提供给IT部门来监视系统及后台处理程序，如电子邮件的病毒扫描通常就归属于这一范畴。

(1) WhatkindsoftechnologiesdotheCloudComputingvendorscombinetoprovideservice?()

A. virtualization,automatedprovisioning,andInternetconnectivity.

B. virtualization,database,andInternetconnectivity.

C. Graphics,database,andInternetconnectivity.

D. virtualreality,Graphics,database.QuestionsandAnswers

(2) Whatdoestheon-demandmodelinclude?()

A Theon-demandmodelincludesaGUIinterfacethatallowsuserstoself-provisionservices.

B. Theon-demandmodelincludesaself-provisioninterfacethatallowsuserstoself-serviceservices.

C. Theon-demandmodelincludesaself-serviceinterfacethatallowsuserstoself-provisionservices.

D. Theon-demandmodelincludesaself-serviceinterfacethatallowsserverstoself-provisionservices.

(3) Whichkindofserviceisthemostwidelyknownandwidelyusedformofcloudcomputing?()

A. PaaS(PlatformasaService).

B. SaaS(SoftwareasaService).

C. IaaS(InfrastructureasaService).

D. Alloftheabove.

(4) Whichkindofserviceisdesignedtoaugmentorreplacethefunctionsofanentiredatacenter？()

A. PaaS(PlatformasaService).

B. SaaS(SoftwareasaService).

C. IaaS(InfrastructureasaService).

D. Alloftheabove.

(5) Whichkindofservicehaseliminatedcustomerworriesaboutapplicationservers,storage,applicationdevelopmentandrelated,commonconcernsofIT？()

A. SaaS(SoftwareasaService).

B. PaaS(PlatformasaService).

C. IaaS(InfrastructureasaService).

D. Alloftheabove.

1. WhatdoweneedtouseCloudComputing?

2. What’sthedifferenceamongthethreetypesofCloudComputing?Problems

There’sakindofsupply-and-demanddynamicthatappliestotechnicalterms—whenafewknowledgeableinsidersarehoardingaword,itmaintainsitsmeaning,butwhenthemassesgetholdofitandabuseit,it’squicklyemptiedofvalue.ReadingMaterialTheCloud:ashortintroduction

Thisiscertainlythecasewith“thecloud,”atermthatusedtomeansomething,andnowmeanseverythingandnothing.“Thecloud”issooverusedbystartupsdesperateforVCmoney,andbybigcompaniesdesperatetolooklikehipstartups,thatITprofessionalsareincreasinglywaryofanythingcloud-related.Itdoesn’thelpthattheimageconjuredbythewordisofsomethingvaporous,flimsy,andfleeting—whatevercloudis,itdoesn'tsoundlikethekindofthingyouwanttoentrustcriticalbusinessfunctionsto.

Despitethefactthateveryoneseemstoseeadifferentshapewhentheystareatit,thereissomethingworthpreservingin“thecloud”asatermthatusefullydescribesoneapproachtowhatisoftencalled“utilitycomputing”,whichlattertermisitselfametaphoricalwayofspeakingaboutabusinessmodelcenteredaroundtheideaofcomputingpowerasaservicelikeelectricalpower.

Infirstdefiningandthendescribingcloudcomputinginthisbriefarticle,myaimistoprovideausefuldefinitionforITprofessionalswhoaretaskedwithexploringcloudservicesasapotentialavenueforfindingnewefficiencies,reducingfixedcosts,tacklingscalingchallenges,andsolvingnovelproblemsatInternetscale.MysecondaryaudiencesforthispieceareITproswhoneedtoquicklyexplain“thecloud”toacluelessCIO,andcluelessCIOswho’drathernothavetorelyonITprostoexplainbuzzwordstothem.

Thisarticletakesahistoricalandcomparativeapproachtothetopicofcloudcomputing.First,I’llintroducethevenerableclient-servermodel,amodelofwhichcloudisjustthelatestinstance,andthenI’llcontrastthecloudwithitsimmediatepredecessor,thegrid.Finally,I’lldescribethethree-tieredmodelofcloudservices.

Oneofthemostcommonquestionsaskedbycloudskepticsis,“isn’tcloudjustclient-server?”Theanswertothisis,yes,itis.Therearemanyproducer-consumerrelationshipsateverylevelofcomputing,fromtheindividualsystemouttothenetwork,thatcanusefullybethoughtofinclient-serverterms.Forinstance,aPC’smainmemoryservesavarietyofclientsscatteredthroughoutthesystemviaDMArequests.Ingeneral,aclient-serverrelationshipischaracterizedbyasingleproducerthatallowsmultipleconsumersaccesstoitsresourcepool.Abriefhistoryofclient-server

Inthisrespect,cloudfitstheclient-servermodel,and,insofarasthetypicalcloudclientisthesameasthetypicalenterpriseclient(i.e.singledesktoporlaptopcomputer),someobservershaveatendencytostopatthislevelofanalysis.But,ofcourse,therealactioninthecloudhappensontheserversideoftheequation,andthat’swherethingsgetinteresting.Butbeforewegetintothecloudinearnest,let’stakeabrieflookbackatclient-server.

Thereareessentiallytwokindsofresourcesthataservercanprovidetoclients:storageandcomputecycles.Client-servermodelscangenerallybecategorizedaccordingtowhichtypeofresourcetheyprovide.

Chronologically,thefirsttypeofclient-serverpairtobecomepopularwasthemainframeandterminal.SincestorageandCPUcyclesweresoexpensive,themainframepooledbothtypesofresourcesandservedthemtothin-clientterminals.WiththeadventofthePCrevolution,whichbroughtmassstorageandcheapCPUstotheaveragecorporatedesktop,thefileservergainedinpopularityaswaytoenabledocumentsharingandarchiving.Truetoitsname,thefileserverservedupstorageresourcestoclientsintheenterprise,whiletheCPUcyclesneededtodoproductiveworkwiththoseresourceswereallproducedandconsumedwithintheconfinesofthePCclient.

The1980salsosawtheriseofthesupercomputer,whichfeaturedalarge,homogenousarrayofprocessorsandwasdesignedtoserveCPUcyclesto“fat-client”workstations.Supercomputerswerelimitedtogovernment(mostlymilitary)andgovernment-sponsoredpartsofacademia,notjustbecausethosesectorsweretheonlyoneswiththeappetiteforthatmuchnumbercrunchingpower,butbecausethosetypesofpublicinstitutionshadpocketsdeepenoughtoaffordthesemachines(itwasvery,veryexpensivetopoolCPUcyclesandservethematascalethatcouldactuallydousefulwork).

ButwhilethesupercomputermarketwasheatingupalongwiththeColdWarthatmuchofitsoutputwenttowardfighting,theseedsofthatmarket’sdestructionwerebeingsownbybothMoore'sLawandtheInternet.

Intheearly1990s,thebuddingInternetfinallyhadenoughcomputersattachedtoitthatacademicsbeganthinkingseriouslyabouthowtoconnectthosemachinestogethertocreatemassive,sharedpoolsofstorageandcomputepowerthatwouldbemuchlargerthanwhatanyoneinstitutioncouldaffordtobuild.Thisiswhentheideaof“thegrid”begantotakeshape.Thegrid,andtheriseofutilitycomputing

Theterm“grid”isametaphordeliberatelydrawnfromtherealmofelectricitygeneration,whereelectricutilitiesprovidepowerovera“grid”networktoclientswhopayonameteredbasisfortheelectricitythattheyconsume.Theideabehindthegridmodel,andtherelatedconceptof“utilitycomputing”,wasthatasufficientlylargenumberofnetworkedcomputerscouldbepooledtogetherlikeagiant,virtualsupercomputerorfileserver,andaccesstothatpoolofcomputeorstorageresourcescouldbesoldinanon-demand,meteredfashion.

Inall,gridcomputingfeaturesalargenumberofnetworked,oftengeographicallyandinstitutionallyseparatenodesthattogethermakeupasharedpoolofcomputeresources.Dataandcomputationalgridsarecharacterizedbyautonomous,homogeneousnodesthatarelooselycoupledandoftenusepublicnetworks.Notethatthegrid’sloosecouplingofnodesisamajorcharacteristicthatdistinguishesitfromthecluster,asimilarmultinodecomputingconceptwithwhichthegridisoftenconfused.Clustersfeaturenodesthatareconnectedbyveryhigh-bandwidthlinks,andthisbandwidthadvantagegivesthemalotmoreaveragecomputepowerpernodethanagridbecausenodesdon’tspendasmuchidletimewaitingondatatoarrive.

Computationalgridsaremorecommonthandatagrids,andapplicationshavetobespeciallywrittenforsuchgridsanddesignedtoscaletoalargenumberofparallelnodes.Atypicalcomputationalgridclientturnstothegridbecauseheneedstorunamassive,compute-intensivejobthatwilloccupyalargesubsetofthosenodesforagivenperiodoftime.Fig.1Thegrid.Differentcoloredjobsbelongtodifferentclients.(OneofthosejobsbelongstotheDepartmentofDefense.)

Gridjobsareoftenruninbatches,whereavailablenodesarepooledtogetherandthenassignedworkthatmonopolizesthemuntilit’sdone.(Note:manygridnodes,likethoseinvolvedintheproject,alsorunlocalclientsoftwaresimultaneouslywiththeirgridjob;butfromthepoint-of-viewofthegrid,thatnodeisstillworkingonasinglejob.)Whenthegridjobiscomplete,thenodesarereleasedbackintothepoolofavailableresources,andarereadyforsomeotherclienttouse.

Onekeyaspectofthegridisthatmultipleinstitutionscansharethesamehardwareresourceswithoutworryingaboutanyoneelseonthegridgainingunauthorizedaccesstotheirdata.Eventhoughthedataisonapubliclyaccessiblegrid,itremainsaccessibleonlytotheclientthatownsit.It’salsothecasethatthegridhardwareitselfoftenhasmanyinstitutionaland/orindividualowners—eachpartycontributescomputeresourcestoasharedpool,andinexchange,contributorscanbidforcyclesfromthatpool.

Thecloudisthesamebasicideaasthegrid,butscaleddowninsomeways,scaledupinothers,andthoroughlydemocratized.Takealookatthediagrambelow,andcontrastitwiththegriddiagramabove.ThecloudFig.2Thecloud.Differentcoloredjobsbelongtodifferentclients.(Oneofthosejobsbelongstoyour18-year-oldnephew.)

Likethegrid,thecloudisautilitycomputingmodelthatinvolvesadynamicallygrowingandshrinkingcollectionofheterogenous,looselycouplednodes,allofwhichareaggregatedtogetherandpresentthemselvestoaclientasasinglepoolofcomputeand/orstorageresources.Butthoughtheserversideofthemodelmaylooksimilar,mostthemajordifferencesbetweencloudandgridstemfromthedifferencesbetweentheirrespectiveclients.

Insteadofafewclientsrunningmassive,multinodejobs,thecloudservicesthousandsormillionsofclients,typicallyservingmultipleclientspernode.Theseclientshavesmall,fleetingtasks(e.g.,databasequeriesorHTTPrequests—thatareoftencomputationallyverylightweightbutpossiblystorage-orbandwidth-intensive).Fig.3CloudvsGrid

Anotherdifferencebetweenthecloudandthegridisthatthegridsarebiasedtowardservingcomputecycles,whilecloudstypicallyoffermoreinthewayofstoragethancycles.Indeed,mostgridswouldbeveryill-suitedtocloudworkloadslikeWebserving,andmostcloudswouldfallfarshortofgridclients’massivecomputeneeds.

Becauseofthenatureoftheirrespectiveclientprofiles,cloudsandgridsalsohavedifferentownershipcharacteristics.Inotedabovethatgridstendtobemulti-institutional,whereinstitutionsand/orindividualsallcontributehardwareresourcesthatarethensharedbyothercontributors.Acloud,incontrast,isalwaysownedbyoneinstitution,regardlessofwhetheruseofthecloudisopentoclientsoutsidethatinstitutionornot(i.e.,whetherthecloudispublic,private,orhybrid).

Cloudservicesareofferedatthreebasiclevels,ortiers,thataredistinguishedbythelevelofabstractionthateachpresentstotheclient.Thesetiersroughlymaptothethreelayersofthestandardhardware/OS/applicationsstackfamiliartoanyonewhousesaPC.Cloudservices:tiersandfears

Thelowestcloudtierisinfrastructure-as-a-service(IaaS),whichlookstotheclientlikeadynamicallyscalablepoolofcomputeand/orstorageresources.ThebasicmeteredunitofIaaSisusuallyeitherasinglevirtualmachine(e.g.,AmazonEC2)oranabstractstorageobjectofacertainsize(e.g.,AmazonS3).

Nextuptheladderofabstractionisplatform-as-a-service(PaaS),whichprovidesAPI-levelaccesstoacloudinfrastructurelayer.ExamplesofPaaSareGoogleAppEngineandF.BecausePaaSofferingsoftencomewrappedinavendor-specificAPI,theuseofthislayerprettymuchlocksyouintoaparticularvendor.It’satthistierthatenterprisecustomersmusttakeseriouslytherisk/rewardtradeoffbetweentheconvenienceandagilityaffordedbyavendor’scloudofferingandthepotentialinconvenienceofbeingunabletoeasilymoveawayfromthatvendor’splatformshouldbusinessortechnicalconsiderationsdemandit.

Thefinalandmostpopulartierofcloudserviceissoftware-as-a-service(SaaS).GoogleAppsandSarethetwoparadigmaticSaaSexamples,andthey’resoubiquitousthatnotmuchmoreneedstobesaidaboutthiscloudtier.

Insofaras