云计算课程第3讲

1上节回顾•从服务器集群到WSC•云数据中心的部署模式•云数据中心的可靠性评级标准•数据中心主要功能和机房组成•为什么需要关注数据中心效能•国内外案例对比，PUE的比拼•绿色数据中心和新能源•OpenComputeProject上海交通大学计算机科学与工程系2016年秋授课人:李超特别副研究员云计算概论IntroductiontoCloudComputing三、虚拟化环境3如何管理复杂性？•虚拟化Virtualization•软件定义SoftwareDefinedSystemHowtomanagecomplexityincomputingsystems?4摘要•虚拟化技术简介–虚拟计算机概念–计算机系统接口–两类重要虚拟机–经典虚拟机分析–案例分析–虚拟化技术应用注：部分slides内容借鉴佛罗里达大学Dr.R.Figueiredo的研究生课程VirtualComputers主要内容参考JSmith的名著VirtualMachines:VersatilePlatformsforSystemsandProcesses5摘要•虚拟化技术简介–虚拟计算机概念–计算机系统接口–两类重要虚拟机–经典虚拟机分析–案例分析–虚拟化技术应用注：部分slides内容借鉴佛罗里达大学Dr.R.Figueiredo的研究生课程VirtualComputers主要内容参考JSmith的名著VirtualMachines:VersatilePlatformsforSystemsandProcesses6物理计算机APhysicalComputer7物理计算机的一般组成•MajorComponentsofatypicalcomputer–Processor,i.e.,CPU–Storage•DRAMmemoryblockssupplyoperandsandholdsresultsofcomputations•Harddisksalsosupplyoperands,holdresults;datatypicallystructuredinafilesystemhierarchy–Communication•Networkinterface–UserInterface•Keyboard,mouse,display,etc8虚拟计算机？•虚拟化(Virtualization)–Decouplecomputationfromphysicalresources•Computation=virtualcomputer=resource•“虚拟(Virtual)”的定义–“Commonalternativetological;oftenusedtorefertotheartificialobjectscreatedbyacomputersystemtohelpthesystemcontrolaccesstosharedresources.”[FreeOnlineDictionaryofComputing]9为什么要虚拟化？•主要动机–Resourcesharingwithsecurityandisolation•Similartomulti-user/multi-programming–Easeofmanagement•Virtual(software)vs.physical(hardware)虚拟化技术整合了服务器、存储、网络和桌面应用，提高了资源利用率和管理灵活度，节省服务器空间和耗电成本，为云计算提供了技术基础，是当前企业IDC建设的发展方向。研究虚拟化技术对电商系统建设和管理具有重要意义10虚拟机VirtualMachines(VM)•Anenablingvirtualcomputertechnology•“Asystem…which…isahardware-softwareduplicateofarealexistingmachine,inwhichanon-trivialsubsetofthevirtualmachine’sinstructionsexecutedirectlyonthehostmachine…”[Goldberg1971]11虚拟计算机的组成（类比物理计算机）•Processor–Virtualmachine•Storage–VM’svirtualmemory–Virtualfilesystems:supplyoperandsandholdresultsofoperations(files,directories)•Communication–Virtualnetworks:allowforcommunicationwithother(virtual,physicalcomputers•Userinterfaces–Remotekeyboard,mouse,display;audio…12经典虚拟机•经典虚拟机的概念追溯至上世纪70年代–SharingofmainframecomputersbymultiplelegacyO/Ss，includingsingle-userO/Sswithoutvirtualmemory(注：虚拟内存的概念上世纪50年代便提出了)•经典虚拟机的实现方式？–“Hosted”VMsarecommon–Virtualdisk,memory,I/Odevices•Stateencapsulatedinfilesstoredinthehost–Avirtualmachinemonitor(VMM)thatimplementsthemechanismsallowingforaHW/SWduplicate13经典虚拟机•CommonISA,O/Ssofdifferenttypes–“Polymorphism”即，多态•Image(镜像，或虚拟机状态“state”)canbecopiesandinstantiatedmanytimes–“Manifolding”即，重用•VMstime-shareaphysicalresource–“Multiplexing”即，复用14虚拟计算机演化•传统虚拟机主要解决单节点物理机的资源共享–面向70年代时的计算机背景–在中央式计算模型下的计算虚拟化•现代经典虚拟机生存在一个深度互联的世界–如今的计算机是网络互联的–在分布式的处理器、内存、硬盘环境下的虚拟化15目前常见虚拟机应用•Pre-packaged,pre-configuredVM–TheentireVMisencapsulatedinasmallnumberoffiles,easilydownloadable–Simpletodeploy,worksonresourcesconfiguredindifferentways：Windows,Linux,MacOS操作系统+Vmware,VirtualBox等虚拟化软件16目前常见虚拟机应用•AmazonElasticComputingCloud(EC2)–ResizablecomputingcapacitywithVMshostedonremoteinfrastructure•Reconfigurewithinminutes•CanscaletothousandsofVMs–Configuretoyourneeds•“Root”accesstoaXen/LinuxVM•Webserviceinterfaceforcontrol–Flexibleandpay-as-you-go:•Memorysize,storage,bandwidth,CPU17摘要•虚拟化技术简介–虚拟计算机概念–计算机系统接口–两类重要虚拟机–经典虚拟机分析–案例分析–虚拟化技术应用注：部分slides内容借鉴佛罗里达大学Dr.R.Figueiredo的研究生课程VirtualComputers主要内容参考JSmith的名著VirtualMachines:VersatilePlatformsforSystemsandProcesses18ComputerSystemHardware19OperatingSystemInterface•Earlysystems–Single-user,single-program–Resources(CPU/Memory/IO)nottime-shared–OSinterfaceprovidesAPIs(applicationprogramminginterface)withbasicfunctionalitytoaccesssystem’sresources•复杂接口的需求–Time-sharing,multiplexing,interactivity20SystemCalls•Multi-user/multi-programming:O/Scontrolsaccesstosharedresources–Processorstypicallysupport(atleast)twooperationmodes:kernel/user–Protectedoperationsonsharedresources•Applicationsaccesssharedresourcesindirectly–ViatheOS,throughsystemcalls21InstructionSetArchitecture•Definesdataandcontrolflow–Storageresourcesthatholddata•Registers,memoryandtheiraddressing–Instructionsthattransformdata•Arithmetic/logic,floatingpoint–Conditional/unconditionalbranches•Registers–General-purpose(maybetyped:integer,FP,segment,etc)–Special-purpose(PC,conditioncodes,processorstatus)22现代系统的指令集架构ISA23系统接口•ISAdefinesthecontractbetweensoftwareandhardware–Butmodernsoftwareapplicationsdonotruninisolation–Typicallyapplicationsrunontopof(anduseservicesfrom)operatingsystems•Examples:–PowerPoint/Windows/x86–OpenOffice/Linux/x8624系统接口示意图25The“User”ISA•UserISA:–ReferstothoseaspectsoftheISAthatarevisibletoanapplicationprogram26The“System”ISA•SystemISA:–ReferstothoseaspectsoftheISAthatarevisibletosupervisorsoftware,suchastheO/S,whichisresponsibleformanaginghardwareresources•OverviewofSystemISA:–PrivilegeLevels–Systemregisters–Instructionsthatmanagekeyresources•Processor(scheduling,time-sharing)•Memory(isolatedaddressspaces)•I/O(e.g.,isolateddiskstoragespace)27•UserISA:Getsapplication’sworkdone–ThisisthesubsetofanISAtargetedbycompilerswhenmappinganalgorithmspecifiedinahigh-levellangua