Cloud Computing Technology

389 Pages·2022·9.77 MB·English

by  Huawei Technologies Co. Ltd.

Official Textbooks for Huawei ICT Academy
CLOUD
COMPUTING
TECHNOLOGY
Huawei Technologies Co., Ltd.
Cloud Computing Technology
Huawei Technologies Co., Ltd.
Cloud Computing
Technology
HuaweiTechnologiesCo.,Ltd.
Hangzhou,Zhejiang,China
ThisworkwassupportedbyHuaweiTechnologiesCo.,Ltd.
ISBN978-981-19-3025-6 ISBN978-981-19-3026-3 (eBook)
https://doi.org/10.1007/978-981-19-3026-3
JointlypublishedwithPosts&TelecomPress,Beijing,China
TheprinteditionisnotforsaleinChina(Mainland).CustomersfromChina(Mainland)pleaseorderthe
printbookfrom:Posts&TelecomPress.
©Posts&TelecomPress2023.Thisbookisanopenaccesspublication.
Open Access This book is licensed under the terms of the Creative Commons Attribution-
NonCommercial-NoDerivatives 4.0 International License (http://creativecommons.org/licenses/by-nc-
nd/4.0/),whichpermitsanynoncommercialuse,sharing,distributionandreproductioninanymediumor
format,aslongasyougiveappropriatecredittotheoriginalauthor(s)andthesource,providealinktothe
CreativeCommonslicenseandindicateifyoumodifiedthelicensedmaterial.Youdonothavepermission
underthislicensetoshareadaptedmaterialderivedfromthisbookorpartsofit.
Theimagesorotherthirdpartymaterialinthisbookareincludedinthebook’sCreativeCommonslicense,
unlessindicatedotherwiseinacreditlinetothematerial.Ifmaterialisnotincludedinthebook'sCreative
Commonslicenseandyourintendeduseisnotpermittedbystatutoryregulationorexceedsthepermitted
use,youwillneedtoobtainpermissiondirectlyfromthecopyrightholder.
Thisworkissubjecttocopyright.Allcommercialrightsarereservedbytheauthor(s),whetherthewhole
orpartofthematerialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustrations,
recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor
informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar
methodology now known or hereafter developed. Regarding these commercial rights a non-exclusive
licensehasbeengrantedtothepublisher.
Theuseofgeneraldescriptivenames,registerednames,trademarks,servicemarks,etc.inthispublication
doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfromtherelevant
protectivelawsandregulationsandthereforefreeforgeneraluse.
Thepublishers,theauthors,andtheeditorsaresafetoassumethattheadviceandinformationinthisbook
arebelievedtobetrueandaccurateatthedateofpublication.Neitherthepublishersnortheauthorsorthe
editorsgiveawarranty,expressedorimplied,withrespecttothematerialcontainedhereinorforany
errorsoromissionsthatmayhavebeenmade.Thepublishersremainneutralwithregardtojurisdictional
claimsinpublishedmapsandinstitutionalaffiliations.
ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSingaporePteLtd.
The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721,
Singapore
Preface
The sudden outbreak of novel coronavirus pneumonia (2019-nCoV) in 2020 has
greatly affected people’s lives. During the severe epidemic, everyone was
quarantined at home and in the community, unable to go to work and school as
usual. As a university teacher, the editor originally worried that normal teaching
couldnotbecarriedout.Fortunately,withthehelpoftheInternetandcloudservices,
even when the campus is closed, teaching and work in the university can still
continue,teacherscanteachonline,andstudentscanlearnonline.Cloudcomputing
technology plays an important role in the information technology that has made a
majorcontributiontothefightagainsttheepidemic.Asfarasteachingisconcerned,
thecommunicationbetweenteachersandstudentsisthroughthecloud:theteacher
uploadstheslidesandteachingmaterialsintothecloud,andthestudentsobtainthe
materials from the cloud. The teaching cloud platform provides various functions
suchassign-in,study,homework,andtest.Thecommunicationamongteachersand
between teachers and students is through instant messaging software such as
WeChat and QQ (the backend of these software is the cloud), and the meeting is
through cloud conference systems such as Zoom, Tencent Meeting, and Webex.
Withthehelpofcloudcomputingtechnology,wecanstillteachandworknormally
duringtheepidemic,andthisbookcanbecompleted.
Cloud computing technology has changed people’s lifestyles, helped improve
people’sconvenienceandqualityoflife,andmadeabetterfuture.Itsemergenceisa
realistic portrayal of “technology changes life and changes the future.” However,
cloud computing technology itself integrates a variety of information technologies
andisrelativelycomplex.It isstill difficult for beginners tohavea more complete
understanding of cloud computing technology. With regard to this reason, East
China Normal University cooperated with Huawei to write this book on the basis
ofHuawei’scertifiedcloudcomputingseriesoftrainingmaterials.
Thereareeightchaptersinthisbook.Chapter1introducesanoverviewofcloud
computing.Itincludescommoncloudcomputingscenariosinlife.Thecharacteris-
tics, definition, origin and development of cloud computing, as well as advantages
andclassificationofcloudcomputingarediscussedinthischapter.Italsomentioned
v
vi Preface
varioustypesofsupportingtechnologiesforcloudcomputingandthreeperspectives
on comprehending the business model, computing model and implementation of
cloud computing. It also presents the state-of-art open source approach in cloud
computing.Chapter2introducesthecloudcomputingsystem,startingfromthefour
aspects of cloud infrastructure mechanism, cloud management mechanism, cloud
security mechanism, and basic cloud architecture, and discusses some of the main
technical mechanisms for building cloud technology architecture. Chapter 3 intro-
duces virtualization technology, focusing on server virtualization technology,
including its basic knowledge and supporting technologies, and discusses some
actual virtualization products or applications based on theoretical knowledge, such
as open-source virtual machine software KVM, Huawei FusionCompute cloud
operatingsystem, and desktop cloud. Chapter 4 introducesthe basic knowledge of
network in cloud computing, including an overview of computer networks, basic
principles of computer networks, network interconnection equipment, network
virtualizationandsoftware-definednetworks,etc., sothat readers canbetter under-
stand some important concepts of computer networks, principles, equipment, and
new network technologies supporting cloud computing. Chapter 5 introduces the
basicknowledgeofstorageincloudcomputingandalsointroducesstorageincloud
computing in detail from the basic knowledge of storage, basic storage units,
network storage, storage reliability technology, storage virtualization, distributed
storage,etc.Chapter6startsfrompractice,introducesthepopularopen-sourcecloud
operating system framework OpenStack, analyzes various components of
OpenStack, discusses its operating mechanism, and enables readers to master the
skillsofimplementingandmanagingOpenStack.Chapter7introducesthecontainer
technology that is widely concerned in cloud computing. It introduces the knowl-
edge of container technology and container orchestration from the aspects of plat-
formarchitecture,basiccorefunctions,network,security,andresourcemanagement
inatheoreticalaswellaspracticalmodel,whichisconvenientforreaderstohavea
comprehensive understanding of Docker and Kubernetes ecosystem. Chapter 8
introducesthedevelopmentstatusofcloudcomputingathomeandabroad,analyzes
and predicts its development trend, and discusses and analyzes the relationship
betweentheInternetofThings,bigdata,artificialintelligence,5Gandotherpopular
cutting-edgetechnologies,andcloudcomputing.Italsointroducesadditionalemerg-
ing technologies, such as edge computing and fog computing, microservices, and
serverlesscomputing.
ThisbookwaseditedbyHuaweiTechnologiesCo.,Ltd.Thespecificauthorsareas
follows:WangWeiformulatedtheoutlineandwasresponsiblefortheoveralldraftof
the book, Zheng Kai was responsible for the main review, and Yang Lei provided
traininghandouts.Chapters1,2,4,and8arewrittenbyZhengKai.Chapters3and5
arewrittenbyHuangLibo,andChaps.6and7arewrittenbyXuYanjun.
In the process of writing this book, the editors have referred to and cited many
worksorpapersbycolleaguesathomeandabroad(seereferencesfordetails),andI
wouldliketoexpressmygratitudetothem.Atthesametime,Isincerelythankthe
trainingteachersandengineersofHuaweifortheirhelpandsupport.
Shanghai,China HuaweiTechnologiesCo.,Ltd.
December2021
Contents
1 IntroductiontoCloudComputingComputing. . . . . . . . . . . . . . . . . 1
1.1 UbiquitousCloudComputing. . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 ThePropertiesofCloudComputing. . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 On-DemandSelf-Service. . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2 ExtensiveNetworkAccess. . . . . . . . . . . . . . . . . . . . . . . 5
1.2.3 ResourcePooling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.4 FastandElasticScaling. . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.5 MeasurableServices. . .. . . .. . . .. . . .. . . .. . . .. . . .. 7
1.3 DefinitionofCloudComputing. . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 TheEmergenceandDevelopmentofCloudComputing. . . . . . . . 12
1.4.1 TheHistoryoftheNetworkandtheInternet. . . . . . . . . . 13
1.4.2 TheHistoryofComputingModels. . . . . . . . . . . . . . . . . 15
1.4.3 TheDrivingForceofCloudComputing. . . . . . . . . . . . . 23
1.4.4 TheDevelopmentofCloudComputing. . . . . . . . . . . . . . 26
1.5 TheAdvantageofCloudComputing. . . . . . . . . . . . . . . . . . . . . 27
1.6 ClassificationofCloudComputing. . . . . . . . . . . . . . . . . . . .. . . 28
1.6.1 ClassificationbyOperatingModel. . . . . . . . . . . . . . . . . 28
1.6.2 ClassificationbyServiceModel. . . . . . . . . . . . . . . . . . . 31
1.7 CloudEnablingTechnology. . . . . . . . . . . . . . . . . . . . . . . . . . . 34
1.7.1 BroadbandNetworkandInternetArchitecture. . . . . . . . . 35
1.7.2 DataCenterTechnology. . . . . . . . . . . . . . . . . . . . . . . . . 36
1.7.3 VirtualizationTechnology. . . . . . . . . . . . . . . . . . . . . . . 37
1.7.4 WebTechnology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
1.7.5 Multi-TenantTechnology. . . . . . . . . . . . . . . . . . . . . . . . 41
1.7.6 ServiceTechnology. . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
1.8 UnderstandCloudComputing. . . . . . . . . . . . . . . . . . . . . . . . . . 44
1.8.1 TheTernaryEpistemologyofCloudComputing. . . . . . . 44
1.8.2 OpenSourceMethodologyofCloudComputing. . . . . . . 50
1.9 Exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
vii
viii Contents
2 CloudComputingSystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.1 CloudInfrastructureMechanism. . . . . . . . . . . . . . . . . . . . . . . . 59
2.1.1 LogicalNetworkBoundary. . . .. . . . . .. . . . . .. . . . . .. 59
2.1.2 VirtualServer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
2.1.3 CloudStorageDevices. . . . . . . . . . . . . . . . . . . . . . . . . . 63
2.1.4 CloudUsageMonitoring. . . . . . . . . . . . . . . . . . . . . . . . 67
2.1.5 ResourceReplication. . . . . . . . . . . . . . . . . . . . . . . . . . . 69
2.2 CloudManagementMechanism. . . . . . . . . . . . . . . . . . . . . . . . . 69
2.2.1 RemoteManagementSystem. . . . . . . . . . . . . . . . . . . . . 70
2.2.2 ResourceManagementSystem. . . . . . . . . . . . . . . . . . . . 72
2.2.3 SLAManagementSystem. . . . . . . . . . . . . . . . . . . . . . . 72
2.2.4 BillingManagementSystem. . . . . . . . . . . . . . . . . . . . . . 73
2.3 CloudSecurityMechanism. . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
2.3.1 Encryption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
2.3.2 Hashing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
2.3.3 DigitalSignature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
2.3.4 PublicKeyInfrastructure. . . . . . . . . . . . . . . . . . . . . . . . 78
2.3.5 IdentityandAccessManagement. . . . . . . . . . . . . . . . . . 80
2.3.6 SingleSignOn. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
2.3.7 Cloud-BasedSecurityGroup. . . . . . . . . . . . . . . . . . . . . 82
2.3.8 HardenedVirtualServerImage. . . . . . . . . . . . . . . . . . . . 83
2.4 BasicCloudArchitecture. . . . .. . . . . . . .. . . . . . . .. . . . . . . .. 84
2.4.1 LoadDistributionArchitecture. . . . . . . . . . . . . . . . . . . . 84
2.4.2 ResourcePoolingArchitecture. . . . . . . . . . . . . . . . . . . . 85
2.4.3 DynamicScalabilityArchitecture. . . . . . . . . . . . . . . . . . 86
2.4.4 ElasticResourceCapacityArchitecture. . . . . . . . . . . . . . 87
2.4.5 ServiceLoadBalancingArchitecture. . . . . . . . . . . . . . . . 88
2.4.6 CloudBurstingArchitecture. . . . . . . . . . . . . . . . . . . . . . 90
2.4.7 ElasticDiskProvisioningArchitecture. . . . . . . . . . . . . . 91
2.4.8 RedundantStorageArchitecture. . . . . . . . . . . . . . . . . . . 92
2.5 Exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
3 VirtualizationTechnology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.1 IntroductiontoVirtualizationTechnology. . . .. . . .. . . . .. . . .. 97
3.1.1 DefinitionofVirtualization. . . . . . . . . . . . . . . . . . . . . . . 97
3.1.2 DevelopmentofVirtualizationTechnology. . . . . . . . . . . 99
3.1.3 AdvantagesofVirtualizationTechnology. . . . . . . . . . . . 100
3.1.4 CommonTypesofVirtualizationTechnology. . . . . . . . . 101
3.2 BasicKnowledgeofServerVirtualization. . . . . . . . . . . . . . . . . 103
3.2.1 SystemVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . 103
3.2.2 ServerVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . 104
3.2.3 TypicalImplementation. . . . . . . . . . . . . . . . . . . . . . . . . 105
3.2.4 FullVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
3.2.5 Paravirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
3.2.6 MainstreamServerVirtualizationTechnology. . . . . . . . . 109
Contents ix
3.3 SupportingTechnologyofServerVirtualization. . . . . . . . . . . . . 110
3.3.1 CPUVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3.3.2 MemoryVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . 112
3.3.3 DeviceandI/OVirtualization. . . . . . . . . . . . . . . . . . . . . 114
3.3.4 StorageVirtualization. . . . .. . . . .. . . . . .. . . . .. . . . .. 116
3.3.5 NetworkVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . 117
3.3.6 DesktopVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . 118
3.4 MainFunctionsofVirtualMachine. . . . . . . . . . . . . . . . . . . . . . 120
3.4.1 VirtualMachineSnapshot. . . . . . . . . . . . . . . . . . . . . . . 120
3.4.2 RapidDeploymentandCloningofVirtualMachines. . . . 121
3.4.3 VirtualMachineBackup. . . . . . .. . . . . . . . . . . . . . . .. . 122
3.4.4 VirtualizationCluster. . . . . . . . . . . . . . . . . . . . . . . . . . . 123
3.4.5 HotAdditionVirtualMachineResources. . .. . . . . . . . .. 125
3.4.6 NUMA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
3.5 KVM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
3.5.1 IntroductiontoKVM. . . . . . . . . . . . . . . . . . . . . . . . . . . 127
3.5.2 KVMVirtualizationTechnology. . . . . . . . . . . . . . . . . . . 128
3.6 FusionCompute. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
3.6.1 IntroductiontoFusionCompute. . . . . . . . . . . . . . . . . . . . 129
3.6.2 FusionComputeComputingVirtualization. . . . . . . . . . . . 132
3.6.3 FusionComputeStorageVirtualization. . . . . . . . . . . . . . 136
3.6.4 FusionComputeNetworkVirtualization. . . . . . . . . . . . . . 138
3.7 DesktopCloud. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
3.7.1 IntroductiontoDesktopCloud. . . . . . . . . . . . . . . . . . . . 139
3.7.2 DesktopCloudArchitectureandKeyTechnologies. . . . . 139
3.7.3 TypicalApplicationCasesofDesktopCloud. . . . . . . . . . 141
3.7.4 IntroductiontoFusionAccess. . . . . . . . . . . . . . . . . . . . . 142
3.8 Exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
4 NetworkBasicsinCloudComputing. . . . . . . . . . . . . . . . . . . . . . . . 145
4.1 ComputerNetworkOverview. . . . . . . . . . . . . . . . . . . . . . . . . . 145
4.1.1 BasicConceptsofComputerNetworks. . . . . . . . . . . . . . 145
4.1.2 TheFormationandDevelopmentofComputer
Networks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
4.1.3 DefinitionandFunctionofComputerNetwork. . . . . . . . . 150
4.1.4 TheCompositionofaComputerNetwork. . . . . . . . . . . . 150
4.1.5 ClassificationofComputerNetworks. . . . . . . . . . . . . . . 151
4.1.6 TopologyStructureofComputerNetwork. . . . . . . . . . . . 155
4.2 NetworkLayeringandEncapsulation. . . . . . . . . . . . . . . . . . . . . 156
4.2.1 NetworkLayeringandEncapsulation. . . . . . . . . . . . . . . 157
4.2.2 PhysicalLayer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
4.2.3 DataLinkLayer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
4.2.4 NetworkLayer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
4.2.5 TransmissionLayer. . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
x Contents
4.2.6 ApplicationLayer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
4.3 NetworkInterconnectionEquipment. . . . . . . . . . . . . . . . . . . . . 162
4.3.1 RepeatersandHubs. . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
4.3.2 BridgesandSwitches. . . . . . . . . . . . . . . . . . . . . . . . . . . 163
4.3.3 Router. . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 165
4.4 NetworkVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
4.4.1 OverviewofNetworkVirtualization. . . . . . . . . . . . . . . . 168
4.4.2 TraditionalNetworkVirtualization. . . . . . . . . . . . . . . . . 168
4.4.3 VirtualNetworkBasedonVirtualSwitch. . . . . . . . . . . . 173
4.4.4 TheNetworkCharacteristicsofHuawei’sVirtualization
Products. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
4.5 Software-DefinedNetwork. . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
4.5.1 IntroductiontoSDN. . . . . .. . . . . . . . . .. . . . . . . . . .. . 185
4.5.2 DevelopmentofSDN. . . . . . . . . . . . . . . . . . . . . . . . . . . 186
4.5.3 SDNArchitecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
4.5.4 SDNKeyTechnology. . . . . . . . . . . . . . . . . . . . . . . . . . 190
4.5.5 TheAdvantageofSDN. . . . . . . . . . . . . . . . . . . . . . . . . 192
4.6 Exercise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
5 StorageBasicsinCloudComputing. . . . . . . . . . . . . . . . . . . . . . . . . 197
5.1 BasicKnowledgeofStorage. . . . . . . . . . . . . . . . . . . . . . . . . . . 197
5.1.1 StorageDevelopmentandTechnologicalEvolution. . . . . 197
5.1.2 Cutting-EdgeStorageTechnologiesandDevelopment
Trends. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
5.1.3 CommonStorageProductsandSolutions. . . . . . . . . . . . 203
5.1.4 DataSecurityTechnologyofCloudStorage. . . . . . . . . . 205
5.2 BasicStorageUnit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
5.2.1 HardDiskDrive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
5.2.2 Solid-StateDrive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
5.3 NetworkStorage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
5.3.1 DAS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
5.3.2 SAN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
5.3.3 NAS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
5.4 StorageReliabilityTechnology. . . . . . . . . . . . . . . . . . . . . . . . . 221
5.4.1 TraditionalRAIDTechnology. . . . . . . . . . . . . . . . . . . . 221
5.4.2 RAID2.0+technology. . . . . . . . . . . . . . . . . . . . . . . . . 225
5.5 StorageVirtualization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
5.5.1 VirtualizationofI/OPaths. . . . . . . . . . . . . . . . . . . . . . . 230
5.5.2 Block-LevelandFile-LevelStorageVirtualization. . . . . . 233
5.5.3 Host-BasedStorageVirtualization. . . . . . . . . . . . . . . . . . 238
5.5.4 StorageVirtualizationBasedonStorageDevices. . . . . . . 239
5.5.5 Network-BasedStorageVirtualization. . . . . . . . . . . . . . . 239
5.5.6 StorageVirtualizationProductsandApplications. . . . . . . 240
5.6 DistributedStorage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
5.6.1 OverviewofCloudStorage. . . . . . . . . . . . . . . . . . . . . . 242