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畢業(yè)設(shè)計(jì)（論文）外文資料原文及譯文原文出處：《CloudComputing》作者：MichaelMiller以下為英文原文BeyondtheDesktop:AnIntroductiontoCloudComputingInaworldthatseesnewtechnologicaltrendsbloomandfadeonalmostadailybasis,onenewtrendpromisesmorelongevity.Thistrendiscalledcloudcomputing,anditwillchangethewayyouuseyourcomputerandtheInternet.Cloudcomputingportendsamajorchangeinhowwestoreinformationandrunapplications.Insteadofrunningprogramsanddataonanindividualdesktopcomputer,everythingishostedinthe“cloud”—anebulousassemblageofcomputersandserversaccessedviatheInternet.Cloudcomputingletsyouaccessallyourapplicationsanddocumentsfromanywhereintheworld,freeingyoufromtheconfinesofthedesktopandmakingiteasierforgroupmembersindifferentlocationstocollaborate.Theemergenceofcloudcomputingisthecomputingequivalentoftheelectricityrevolutionofacenturyago.Beforetheadventofelectricalutilities,everyfarmandbusinessproduceditsownelectricityfromfreestandinggenerators.Aftertheelectricalgridwascreated,farmsandbusinessesshutdowntheirgeneratorsandboughtelectricityfromtheutilities,atamuchlowerprice(andwithmuchgreaterreliability)thantheycouldproduceontheirown.Lookforthesametypeofrevolutiontooccurascloudcomputingtakeshold.Thedesktop-centricnotionofcomputingthatweholdtodayisboundtofallbythewaysideaswecometoexpecttheuniversalaccess,24/7reliability,andubiquitouscollaborationpromisedbycloudcomputing.Itisthewayofthefuture.CloudComputing:WhatItIs—andWhatItIsn’tWithtraditionaldesktopcomputing,youruncopiesofsoftwareprogramsoneachcomputeryouown.Thedocumentsyoucreatearestoredonthecomputeronwhichtheywerecreated.Althoughdocumentscanbeaccessedfromothercomputersonthenetwork,theycan’tbeaccessedbycomputersoutsidethenetwork.ThewholesceneisPC-centric.Withcloudcomputing,thesoftwareprogramsyouusearen’trunfromyourpersonalcomputer,butareratherstoredonserversaccessedviatheInternet.Ifyourcomputercrashes,thesoftwareisstillavailableforotherstouse.Samegoesforthedocumentsyoucreate;they’restoredonacollectionofserversaccessedviatheInternet.Anyonewithpermissioncannotonlyaccessthedocuments,butcanalsoeditandcollaborateonthosedocumentsinrealtime.Unliketraditionalcomputing,thiscloudcomputingmodelisn’tPC-centric,it’sdocument-centric.WhichPCyouusetoaccessadocumentsimplyisn’timportant.Butthat’sasimplification.Let’slookinmoredetailatwhatcloudcomputingis—and,justasimportant,whatitisn’t.WhatCloudComputingIsn’tFirst,cloudcomputingisn’tnetworkcomputing.Withnetworkcomputing,applications/documentsarehostedonasinglecompany’sserverandaccessedoverthecompany’snetwork.Cloudcomputingisalotbiggerthanthat.Itencompassesmultiplecompanies,multipleservers,andmultiplenetworks.Plus,unlikenetworkcomputing,cloudservicesandstorageareaccessiblefromanywhereintheworldoveranInternetconnection;withnetworkcomputing,accessisoverthecompany’snetworkonly.Cloudcomputingalsoisn’ttraditionaloutsourcing,whereacompanyfarmsout(subcontracts)itscomputingservicestoanoutsidefirm.Whileanoutsourcingfirmmighthostacompany’sdataorapplications,thosedocumentsandprogramsareonlyaccessibletothecompany’semployeesviathecompany’snetwork,nottotheentireworldviatheInternet.So,despitesuperficialsimilarities,networkingcomputingandoutsourcingarenotcloudcomputing.WhatCloudComputingIsKeytothedefinitionofcloudcomputingisthe“cloud”itself.Forourpurposes,thecloudisalargegroupofinterconnectedcomputers.Thesecomputerscanbepersonalcomputersornetworkservers;theycanbepublicorprivate.Forexample,谷歌hostsacloudthatconsistsofbothsmallishPCsandlargerservers.谷歌’scloudisaprivateone(thatis,谷歌ownsit)thatispubliclyaccessible(by谷歌’susers).Thiscloudofcomputersextendsbeyondasinglecompanyorenterprise.Theapplicationsanddataservedbythecloudareavailabletobroadgroupofusers,cross-enterpriseandcross-platform.AccessisviatheInternet.AnyauthorizedusercanaccessthesedocsandappsfromanycomputeroveranyInternetconnection.And,totheuser,thetechnologyandinfrastructurebehindthecloudisinvisible.Itisn’tapparent(and,inmostcasesdoesn’tmatter)whethercloudservicesarebasedonHTTP,HTML,XML,JavaScript,orotherspecifictechnologies.Itmighthelptoexaminehowoneofthepioneersofcloudcomputing,谷歌,perceivesthetopic.From谷歌’sperspective,therearesixkeypropertiesofcloudcomputing:·Cloudcomputingisuser-centric.Onceyouasauserareconnectedtothecloud,whateverisstoredthere—documents,messages,images,applications,whatever—becomesyours.Inaddition,notonlyisthedatayours,butyoucanalsoshareitwithothers.Ineffect,anydevicethataccessesyourdatainthecloudalsobecomesyours.·Cloudcomputingistask-centric.Insteadoffocusingontheapplicationandwhatitcando,thefocusisonwhatyouneeddoneandhowtheapplicationcandoitforyou.,Traditionalapplications—wordprocessing,spreadsheets,email,andsoon—arebecominglessimportantthanthedocumentstheycreate.·Cloudcomputingispowerful.ConnectinghundredsorthousandsofcomputerstogetherinacloudcreatesawealthofcomputingpowerimpossiblewithasingledesktopPC.·Cloudcomputingisaccessible.Becausedataisstoredinthecloud,userscaninstantlyretrievemoreinformationfrommultiplerepositories.You’renotlimitedtoasinglesourceofdata,asyouarewithadesktopPC.·Cloudcomputingisintelligent.Withallthevariousdatastoredonthecomputersinacloud,dataminingandanalysisarenecessarytoaccessthatinformationinanintelligentmanner.·Cloudcomputingisprogrammable.Manyofthetasksnecessarywithcloudcomputingmustbeautomated.Forexample,toprotecttheintegrityofthedata,informationstoredonasinglecomputerinthecloudmustbereplicatedonothercomputersinthecloud.Ifthatonecomputergoesoffline,thecloud’sprogrammingautomaticallyredistributesthatcomputer’sdatatoanewcomputerinthecloud.Allthesedefinitionsbehindus,whatconstitutescloudcomputingintherealworld?Asyou’lllearnthroughoutthisbook,araftofweb-hosted,Internet-accessible,group-collaborativeapplicationsarecurrentlyavailable,withmanymoreontheway.Perhapsthebestandmostpopularexamplesofcloudcomputingapplicationstodayarethe谷歌familyofapplications—谷歌Docs&Spreadsheets,谷歌Calendar,Gmail,Picasa,andthelike.Alloftheseapplicationsarehostedon谷歌’sservers,areaccessibletoanyuserwithanInternetconnection,andcanbeusedforgroupcollaborationfromanywhereintheworld.Inshort,cloudcomputingenablesashiftfromthecomputertotheuser,fromapplicationstotasks,andfromisolateddatatodatathatcanbeaccessedfromanywhereandsharedwithanyone.Theusernolongerhastotakeonthetaskofdatamanagement;hedoesn’tevenhavetorememberwherethedatais.Allthatmattersisthatthedataisinthecloud,andthusimmediatelyavailabletothatuserandtootherauthorizedusers.FromCollaborationtotheCloud:AShortHistoryofCloudComputingCloudcomputinghasasitsantecedentsbothclient/servercomputingandpeer-to-peerdistributedcomputing.It’sallamatterofhowcentralizedstoragefacilitatescollaborationandhowmultiplecomputersworktogethertoincreasecomputingpower.Client/ServerComputing:CentralizedApplicationsandStorageIntheantediluviandaysofcomputing(pre-1980orso),everythingoperatedontheclient/servermodel.Allthesoftwareapplications,allthedata,andallthecontrolresidedonhugemainframecomputers,otherwiseknownasservers.Ifauserwantedtoaccessspecificdataorrunaprogram,hehadtoconnecttothemainframe,gainappropriateaccess,andthendohisbusinesswhileessentially“renting”theprogramordatafromtheserver.Usersconnectedtotheserverviaacomputerterminal,sometimescalledaworkstationorclient.Thiscomputerwassometimescalledadumbterminalbecauseitdidn’thavealot(ifany!)memory,storagespace,orprocessingpower.Itwasmerelyadevicethatconnectedtheusertoandenabledhimtousethemainframecomputer.Usersaccessedthemainframeonlywhengrantedpermission,andtheinformationtechnology(IT)staffweren’tinthehabitofhandingoutaccesscasually.Evenonamainframecomputer,processingpowerislimited—andtheITstaffweretheguardiansofthatpower.Accesswasnotimmediate,norcouldtwousersaccessthesamedataatthesametime.Beyondthat,usersprettymuchhadtotakewhatevertheITstaffgavethem—withnovariations.Wanttocustomizeareporttoshowonlyasubsetofthenormalinformation?Can’tdoit.Wanttocreateanewreporttolookatsomenewdata?Youcan’tdoit,althoughtheITstaffcan—butontheirschedule,whichmightbeweeksfromnow.Thefactis,whenmultiplepeoplearesharingasinglecomputer,evenifthatcomputerisahugemainframe,youhavetowaityourturn.Needtorerunafinancialreport?Noproblem—ifyoudon’tmindwaitinguntilthisafternoon,ortomorrowmorning.Thereisn’talwaysimmediateaccessinaclient/serverenvironment,andseldomisthereimmediategratification.Sotheclient/servermodel,whileprovidingsimilarcentralizedstorage,differedfromcloudcomputinginthatitdidnothaveauser-centricfocus;withclient/servercomputing,allthecontrolrestedwiththemainframe—andwiththeguardiansofthatsinglecomputer.Itwasnotauser-enablingenvironment.Peer-to-PeerComputing:SharingResourcesAsyoucanimagine,accessingaclient/serversystemwaskindofa“hurryupandwait”experience.Theserverpartofthesystemalsocreatedahugebottleneck.Allcommunicationsbetweencomputershadtogothroughtheserverfirst,howeverinefficientthatmightbe.Theobviousneedtoconnectonecomputertoanotherwithoutfirsthittingtheserverledtothedevelopmentofpeer-to-peer(P2P)computing.P2Pcomputingdefinesanetworkarchitectureinwhicheachcomputerhasequivalentcapabilitiesandresponsibilities.Thisisincontrasttothetraditionalclient/servernetworkarchitecture,inwhichoneormorecomputersarededicatedtoservingtheothers.(Thisrelationshipissometimescharacterizedasamaster/slaverelationship,withthecentralserverasthemasterandtheclientcomputerastheslave.)P2Pwasanequalizingconcept.IntheP2Penvironment,everycomputerisaclientandaserver;therearenomastersandslaves.Byrecognizingallcomputersonthenetworkaspeers,P2Penablesdirectexchangeofresourcesandservices.Thereisnoneedforacentralserver,becauseanycomputercanfunctioninthatcapacitywhencalledontodoso.P2Pwasalsoadecentralizingconcept.Controlisdecentralized,withallcomputersfunctioningasequals.Contentisalsodispersedamongthevariouspeercomputers.Nocentralizedserverisassignedtohosttheavailableresourcesandservices.PerhapsthemostnotableimplementationofP2PcomputingistheInternet.Manyoftoday’susersforget(orneverknew)thattheInternetwasinitiallyconceived,underitsoriginalARPAnetguise,asapeer-to-peersystemthatwouldsharecomputingresourcesacrosstheUnitedStates.ThevariousARPAnetsites—andthereweren’tmanyofthem—wereconnectedtogethernotasclientsandservers,butasequals.TheP2PnatureoftheearlyInternetwasbestexemplifiedbytheUsenetnetwork.Usenet,whichwascreatedbackin1979,wasanetworkofcomputers(accessedviatheInternet),eachofwhichhostedtheentirecontentsofthenetwork.Messageswerepropagatedbetweenthepeercomputers;usersconnectingtoanysingleUsenetserverhadaccesstoall(orsubstantiallyall)themessagespostedtoeachindividualserver.Althoughtheusers’connectiontotheUsenetserverwasofthetraditionalclient/servernature,therelationshipbetweentheUsenetserverswasdefinitelyP2P—andpresagedthecloudcomputingoftoday.Thatsaid,noteverypartoftheInternetisP2Pinnature.WiththedevelopmentoftheWorldWideWebcameashiftawayfromP2Pbacktotheclient/servermodel.Ontheweb,eachwebsiteisservedupbyagroupofcomputers,andsites’visitorsuseclientsoftware(webbrowsers)toaccessit.Almostallcontentiscentralized,allcontroliscentralized,andtheclientshavenoautonomyorcontrolintheprocess.DistributedComputing:ProvidingMoreComputingPowerOneofthemostimportantsubsetsoftheP2Pmodelisthatofdistributedcomputing,whereidlePCsacrossanetworkoracrosstheInternetaretappedtoprovidecomputingpowerforlarge,processor-intensiveprojects.It’sasimpleconcept,allaboutcyclesharingbetweenmultiplecomputers.Apersonalcomputer,runningfull-out24hoursaday,7daysaweek,iscapableoftremendouscomputingpower.Mostpeopledon’tusetheircomputers24/7,however,soagoodportionofacomputer’sresourcesgounused.Distributedcomputingusesthoseresources.Whenacomputerisenlistedforadistributedcomputingproject,softwareisinstalledonthemachinetorunvariousprocessingactivitiesduringthoseperiodswhenthePCistypicallyunused.Theresultsofthatspare-timeprocessingareperiodicallyuploadedtothedistributedcomputingnetwork,andcombinedwithsimilarresultsfromotherPCsintheproject.Theresult,ifenoughcomputersareinvolved,simulatestheprocessingpowerofmuchlargermainframesandsupercomputers—whichisnecessaryforsomeverylargeandcomplexcomputingprojects.Forexample,geneticresearchrequiresvastamountsofcomputingpower.Lefttotraditionalmeans,itmighttakeyearstosolveessentialmathematicalproblems.Byconnectingtogetherthousands(ormillions)ofindividualPCs,morepowerisappliedtotheproblem,andtheresultsareobtainedthatmuchsooner.Distributedcomputingdatesbackto1973,whenmultiplecomputerswerenetworkedtogetherattheXeroxPARClabsandwormsoftwarewasdevelopedtocruisethroughthenetworklookingforidleresources.Amorepracticalapplicationofdistributedcomputingappearedin1988,whenresearchersattheDEC(DigitalEquipmentCorporation)SystemResearchCenterdevelopedsoftwarethatdistributedtheworktofactorlargenumbersamongworkstationswithintheirlaboratory.By1990,agroupofabout100users,utilizingthissoftware,hadfactoreda100-digitnumber.By1995,thissameefforthadbeenexpandedtothewebtofactora130-digitnumber.Itwasn’tlongbeforedistributedcomputinghittheInternet.ThefirstmajorInternet-baseddistributedcomputingprojectwas,launchedin1997,whichemployedthousandsofpersonalcomputerstocrackencryptioncodes.EvenbiggerwasSETI@home,launchedinMay1999,whichlinkedtogethermillionsofindividualcomputerstosearchforintelligentlifeinouterspace.Manydistributedcomputingprojectsareconductedwithinlargeenterprises,usingtraditionalnetworkconnectionstoformthedistributedcomputingnetwork.Other,larger,projectsutilizethecomputersofeverydayInternetusers,withthecomputingtypicallytakingplaceoffline,andthenuploadedonceadayviatraditionalconsumerInternetconnections.CollaborativeComputing:WorkingasaGroupFromtheearlydaysofclient/servercomputingthroughtheevolutionofP2P,therehasbeenadesireformultipleuserstoworksimultaneouslyonthesamecomputer-basedproject.Thistypeofcollaborativecomputingisthedrivingforcebehindcloudcomputing,buthasbeenaroundformorethanadecade.EarlygroupcollaborationwasenabledbythecombinationofseveraldifferentP2Ptechnologies.Thegoalwas(andis)toenablemultipleuserstocollaborateongroupprojectsonline,inrealtime.Tocollaborateonanyproject,usersmustfirstbeabletotalktooneanother.Intoday’senvironment,thismeansinstantmessagingfortext-basedcommunication,withoptionalaudio/telephonyandvideocapabilitiesforvoiceandpicturecommunication.Mostcollaborationsystemsofferthecompleterangeofaudio/videooptions,forfull-featuredmultiple-uservideoconferencing.Inaddition,usersmustbeabletosharefilesandhavemultipleusersworkonthesamedocumentsimultaneously.Real-timewhiteboardingisalsocommon,especiallyincorporateandeducationenvironments.Earlygroupcollaborationsystemsrangedfromtherelativelysimple(LotusNotesandMicrosoftNetMeeting)totheextremelycomplex(thebuilding-blockarchitectureoftheGrooveNetworkssystem).Mostweretargetedatlargecorporations,andlimitedtooperationoverthecompanies’privatenetworks.CloudComputing:TheNextStepinCollaborationWiththegrowthoftheInternet,therewasnoneedtolimitgroupcollaborationtoasingleenterprise’snetworkenvironment.Usersfrommultiplelocationswithinacorporation,andfrommultipleorganizations,desiredtocollaborateonprojectsthatcrossedcompanyandgeographicboundaries.Todothis,projectshadtobehousedinthe“cloud”oftheInternet,andaccessedfromanyInternet-enabledlocation.Theconceptofcloud-baseddocumentsandservicestookwingwiththedevelopmentoflargeserverfarms,suchasthoserunby谷歌andothersearchcompanies.谷歌alreadyhadacollectionofserversthatitusedtopoweritsmassivesearchengine;whynotusethatsamecomputingpowertodriveacollectionofweb-basedapplications—and,intheprocess,provideanewlevelofInternet-basedgroupcollaboration?That’sexactlywhathappened,although谷歌wasn’ttheonlycompanyofferingcloudcomputingsolutions.Ontheinfrastructureside,IBM,SunSystems,andotherbigironprovidersareofferingthehardwarenecessarytobuildcloudnetworks.Onthesoftwareside,dozensofcompaniesaredevelopingcloud-basedapplicationsandstorageservices.Today,peopleareusingcloudservicesandstoragetocreate,share,find,andorganizeinformationofalldifferenttypes.Tomorrow,thisfunctionalitywillbeavailablenotonlytocomputerusers,buttousersofanydevicethatconnectstotheInternet—mobilephones,portablemusicplayers,evenautomobilesandhometelevisionsets.TheNetworkIstheComputer:HowCloudComputingWorksSunMicrosystems’ssloganis“Thenetworkisthecomputer,”andthat’sasgoodasanytodescribehowcloudcomputingworks.Inessence,anetworkofcomputersfunctionsasasinglecomputertoservedataandapplicationstousersovertheInternet.Thenetworkexistsinthe“cloud”ofIPaddressesthatweknowastheInternet,offersmassivecomputingpowerandstoragecapability,andenableswidescalegroupcollaboration.Butthat’sthesimpleexplanation.Let’stakealookathowcloudcomputingworksinmoredetail.UnderstandingCloudArchitectureThekeytocloudcomputingisthe“cloud”—amassivenetworkofserversorevenindividualPCsinterconnectedinagrid.Thesecomputersruninparallel,combiningtheresourcesofeachtogeneratesupercomputing-likepower.What,exactly,isthe“cloud”?Putsimply,thecloudisacollectionofcomputersandserversthatarepubliclyaccessibleviatheInternet.Thishardwareistypicallyownedandoperatedbyathirdpartyonaconsolidatedbasisinoneormoredatacenterlocations.Themachinescanrunanycombinationofoperatingsystems;it’stheprocessingpowerofthemachinesthatmatter,notwhattheirdesktopslooklike.AsshowninFigure1.1,individualusersconnecttothecloudfromtheirownpersonalcomputersorportabledevices,overtheInternet.Totheseindividualusers,thecloudisseenasasingleapplication,device,ordocument.Thehardwareinthecloud(andtheoperatingsystemthatmanagesthehardwareconnections)isinvisible.FIGURE1.1Howusersconnecttothecloud.Thiscloudarchitectureisdeceptivelysimple,althoughitdoesrequiresomeintelligentmanagementtoconnectallthosecomputerstogetherandassigntaskprocessingtomultitudesofusers.AsyoucanseeinFigure1.2,itallstartswiththefront-endinterfaceseenbyindividualusers.Thisishowusersselectataskorservice(eitherstartinganapplicationoropeningadocument).Theuser’srequestthengetspassedtothesystemmanagement,whichfindsthecorrectresourcesandthencallsthesystem’sappropriateprovisioningservices.Theseservicescarveoutthenecessaryresourcesinthecloud,launchtheappropriatewebapplication,andeithercreatesoropenstherequesteddocument.Afterthewebapplicationislaunched,thesystem’smonitoringandmeteringfunctionstracktheusageofthecloudsothatresourcesareapportionedandattributedtotheproperuser(s).FIGURE1.2Thearchitecturebehindacloudcomputingsystem.Asyoucansee,keytothenotionofcloudcomputingistheautomationofmanymanagementtasks.Thesystemisn’tacloudifitrequireshumanmanagementtoallocateprocessestoresources.Whatyouhaveinthisinstanceismerelyatwenty-first-centuryversionofold-fashioneddatacenter–basedclient/servercomputing.Forthesystemtoattaincloudstatus,manualmanagementmustbereplacedbyautomatedprocesses.UnderstandingCloudStorageOneoftheprimaryusesofcloudcomputingisfordatastorage.Withcloudstorage,dataisstoredonmultiplethird-partyservers,ratherthanonthededicatedserversusedintraditionalnetworkeddatastorage.Whenstoringdata,theuserseesavirtualserver—thatis,itappearsasifthedataisstoredinaparticularplacewithaspecificname.Butthatplacedoesn’texistinreality.It’sjustapseudonymusedtoreferencevirtualspacecarvedoutofthecloud.Inreality,theuser’sdatacouldbestoredonanyoneormoreofthecomputersusedtocreatethecloud.Theactualstoragelocationmayevendifferfromdaytodayorevenminutetominute,astheclouddynamicallymanagesavailablestoragespace.Buteventhoughthelocationisvirtual,theuserseesa“static”locationforhisdata—andcanactuallymanagehisstoragespaceasifitwereconnectedtohisownPC.Cloudstoragehasbothfinancialandsecurity-associatedadvantages.Financially,virtualresourcesinthecloudaretypicallycheaperthandedicatedphysicalresourcesconnectedtoapersonalcomputerornetwork.Asforsecurity,datastoredinthecloudissecurefromaccidentalerasureorhardwarecrashes,becauseitisduplicatedacrossmultiplephysicalmachines;sincemultiplecopiesofthedataarekeptcontinually,thecloudcontinuestofunctionasnormalevenifoneormoremachinesgooffline.Ifonemachinecrashes,thedataisduplicatedonothermachinesinthecloud.UnderstandingCloudServicesAnyweb-basedapplicationorserviceofferedviacloudcomputingiscalledacloudservice.Cloudservicescanincludeanythingfromcalendarandcontactapplicationstowordprocessingandpresentations.Almostalllargecomputingcompaniestoday,from谷歌toAmazontoMicrosoft,aredevelopingvarioustypesofcloudservices.Withacloudservice,theapplicationitselfishostedinthecloud.AnindividualuserrunstheapplicationovertheInternet,typicallywithinawebbrowser.Thebrowseraccessesthecloudserviceandaninstanceoftheapplicationisopenedwithinthebrowserwindow.Oncelaunched,theweb-basedapplicationoperatesandbehaveslikeastandarddesktopapplication.Theonlydifferenceisthattheapplicationandtheworkingdocumentsremainonthehost’scloudservers.Cloudservicesoffermanyadvantages.Iftheuser’sPCcrashes,itdoesn’taffecteitherthehostapplicationortheopendocument;bothremainunaffectedinthecloud.Inaddition,anindividualusercanaccesshisapplicationsanddocumentsfromanylocationonanyPC.Hedoesn’thavetohaveacopyofeveryappandfilewithhimwhenhemovesfromofficetohometoremotelocation.Finally,becausedocumentsarehostedinthecloud,multipleuserscancollaborateonthesamedocumentinrealtime,usinganyavailableInternetconnection.Documentsarenolongermachine-centric.Instead,they’realwaysavailabletoanyauthorizeduser.CompaniesintheCloud:CloudComputingTodayWe’recurrentlyintheearlydaysofthecloudcomputingrevolution.Althoughmanycloudservicesareavailabletoday,moreandmoreinterestingapplicationsarestillindevelopment.Thatsaid,cloudcomputingtodayisattractingthebestandbiggestcompaniesfromacrossthecomputingindustry,allofwhomhopetoestablishprofitablebusinessmodelsbasedinthecloud.Asdiscussedearlierinthischapter,perhapsthemostnoticeablecompanycurrentlyembracingthecloudcomputingmodelis谷歌.Asyou’llseethroughoutthisbook,谷歌offersapowerfulcollectionofweb-basedapplications,allservedviaitscloudarchitecture.Whetheryouwantcloud-basedwordprocessing(谷歌Docs),presentationsoftware(谷歌Presentations),email(Gmail),orcalendar/schedulingfunctionality(谷歌Calendar),谷歌hasanoffering.Andbestofall,谷歌isadeptingettingallofitsweb-basedapplicationstointerfacewitheachother;theircloudservicesareinterconnectedtotheuser’sbenefit.Othermajorcompaniesarealsoinvolvedinthedevelopmentofcloudservices.Microsoft,forexample,offersitsWindowsLivesuiteofweb-basedapplications,aswellastheLiveMeshinitiativethatpromisestolinktogetheralltypesofdevices,data,andapplicationsinacommoncloud-basedplatform.AmazonhasitsElasticComputeCloud(EC2),awebservicethatprovidescloud-basedresizablecomputingcapacityforapplicationdevelopers.IBMhasestablishedaCloudComputingCentertodelivercloudservicesandresearchtoclients.Andnumeroussmallercompanieshavelaunchedtheirownwebbasedapplications,primarily(butnotexclusively)toexploitthecollaborativenatureofcloudservices.Asweworkthroughthisbook,we’llexaminemanyofthesecompaniesandtheirofferings.Allyouneedtoknowfornowisthatthere’sabigfutureincloudcomputing—andeverybody’sjumpingonthebandwagon.WhyCloudComputingMattersWhyiscloudcomputingimportant?Therearemanyimplicationsofcloudtechnology,forbothdevelopersandendusers.Fordevelopers,cloudcomputingprovidesincreasedamountsofstorageandprocessingpowertoruntheapplicationstheydevelop.Cloudcomputingalsoenablesnewwaystoaccessinformation,processandanalyzeda