云计算平台虚拟机.docx

云计算平台虚拟机.docx

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云计算平台虚拟机

AnEvaluationofKVMforUseinCloudComputing

M.FENN,M.A.MURPHY,J.MARTIN,andS.GOASGUEN

ClemsonUniversity

InthispaperwedescribeavirtualclusterbasedontheKernel-basedVirtualMachine（KVMasanalternativetoVMWareandXen.Specicallyweshowhowthevirtualclusterisbuiltandtailoredtotvirtualorganizations.Thetechniquepresentedinthispaper,knownastheVirtualOrganizationClusterModel,showsgreatpotentialforcloudcomputing.Inourimplementation,weusedaminimalistinstallationofSlackwareLinux12on14computenodes,ensuringminimalhostoverhead.OurprototypeVirtualOrganizationClusteriscomposedof28virtualcomputesnodes,eachrunningCentOS5.1withCondor,andMPI.Resultsoftestingtheprototypewereencouraging,withtheexceptionofnetworkperformance.

CategoriesandSubjectDescriptors:

C.4[ComputerSystemsOrganization]:

PerformanceofSystemsDesignstudies;Performanceattributes;C.2.4[Computer-CommunicationNet-works]:

DistributedSystems

GeneralTerms:

Design,Experimentation,Measurement,Performance

AdditionalKeyWordsandPhrases:

VirtualMachines,KVM,High-PerformanceComputing

1.INTRODUCTION

Acurrentprobleminscienticcomputingisthattheexpertiseneededtodeployandmaintainaclusterremainsscarcedespiterecentdeclinesinhardwarecosts.Smallerresearchgroupsmaynotbeabletoaordtohavetheirownclusters,andpurchasingtimeonanexistingclusterraisesconcernssuchasvendorlock-inanddatasecurity.

Inthispaper,wepresentacloudcomputingmodelwhichdenesaminimumspecicationforacomputecluster.Thiscluster'ssolepurposeistohostothercom-puteclustersthroughvirtualization.Inthisway,aVirtualizationServiceProvider（VSPcansellcomputepowerwithouthavingtodirectlymaintaineachend-user'sparticularapplication.

Similarly,VirtualOrganizations（VO'scanpurchasecomputepowerfromVSP'swithouthavingtoworryabouthardwareorsoftwarecompatibility.AVOisfreetodevelopamodelclusterlocally,perhapsevenonapersonalworkstation,testit,and

Authors'address:

SchoolofComputing,ClemsonUniversity,Clemson,SC29634-0974,USA.{mfenn,mamurph,jim.martin,sebgoa}@cs.clemson.edu

ThismaterialisbaseduponworksupportedunderaNationalScienceFoundationGraduateRe-searchFellowship.

Permissiontomakedigital/hardcopyofallorpartofthismaterialwithoutfeeforpersonalorclassroomuseprovidedthatthecopiesarenotmadeordistributedforprotorcommercialadvantage,theACMcopyright/servernotice,thetitleofthepublication,anditsdateappear,andnoticeisgiventhatcopyingisbypermissionoftheACM,Inc.Tocopyotherwise,torepublish,topostonservers,ortoredistributetolistsrequirespriorspecicpermissionand/orafee.

c20YYACM1529-3785/20YY/0700-0001$5.00

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.

2·M.Fennetal.

（aType1（bType2

Fig.1.Hypervisors

thendeployittoaVSP'shardwarewithreasonableassurancesthattheoperatingenvironmentwillbefullycompatible.

Wewillrstprovideabriefoverviewofvirtualizationtechnologies,followedbyadescriptionofourmodelvirtualcluster.Then,wewilldenetheinfrastructureforwhichanVSPwouldberesponsible.Finally,wewillpresentsomeresultsofamodelclusterconstructedattheCyberinfrastructureResearchLaboratoryatClemsonUniversity.

2.VIRTUALIZATIONMODEL

Inessence,virtualizationismakingonecomputerappeartobemultiplecomputers.[Jones2006]Virtualizationisaccomplishedwithaprogramcalledahypervisor,whilesystemsrunningunderahypervisorareknownasvirtualmachines（VMs.Therearetwobasictypesofhypervisor[IBM2005]:

Type1hypervisorsdirectlyinterfacewiththesystemhardware.Alloperatingsystemsruninsideavirtualmachine.Thereisusuallyaspecial,privilegedvirtualmachinethatcanmanagetheothers.Xenisanexampleofthistypeofhypervisor.Type2hypervisorsrunasanormalprograminsideanormaloperatingsystem.ThisOSisknownasthehost.EachguestOSrunsasaprocessinthehostOS.Theseprocessescanbemanipulatedjustlikeanyotherprocess.VMWareandKVMareexamplesofthistypeofhypervisor.

SeeFigure1foracomparisonofType1and2hypervisors.

AstrictType2hypervisorrequiresthatallI/Odevicesbeemulatedcompletelyinsoftware,resultinginaddedoverheadforI/Ocalls.Paravirtualizationallowsthevirtualmachinetomakecallsdirectlytothehypervisor,resultinginpotentiallyincreasedeciency.Paravirtualizationrequiresmodicationstotheguestkernel.[IBM2005]

SeeTableIforacomparisonofKVMandXen.

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AnEvaluationofKVMforUseinCloudComputing·3

TableI.KVMvs.Xen

KVMXen

Type1HypervisorType2Hypervisor

HostisaprivilegedguestHostdirectlyonhardware

UnprivilegedguestsGuestshaveuserprivileges

x86ringabstractionUNIXprocessabstraction

ParavirtualizedguestsUnmodifiedguests

2.1Kernel-basedVirtualMachine（KVM

TheKernel-basedVirtualMachine（KVMisaType2hypervisormaintainedbyQumranet,Inc[Habib2008][Qumranet2006].KVMisbasedontheQEMUemu-latorandderivesallitsmanagementtoolsfromQEMU.ThemainfocusofKVMdevelopmentistousethex86VTextensions,whichallowvirtualmachinestomakesystemcalls[vanDoorn2006].KVMversionsnewerthanKVM-62havesupportforparavirtualizedLinuxguests,butwedidnotutilizethiscapabilityinourinitialprototype.

KVMusesasetofLinuxkernelmodulestoprovideVTsupport.KVMcanrunonastockLinuxkernelthatis:

（anewenoughand（bhashadtheKVMmodulesbuiltforit.Incontrast,XenrequiresaheavilypatchedLinuxkernel,onwhichdevelopmentlagsbehindthemainlinekernel.

KVMsupportstheQEMUCopy-on-write（QCOWdiskimageformat,allowingittosupportasnapshotmodeforitsdiskI/Ooperations.Insnapshotmode,alldiskwritesaredirectedtoatemporaryle,andchangesarenotpersistedtotheoriginaldiskimagele.MultipleVM'scanberunfromonediskimage,somewhatmitigatingthehugestoragerequirementsassociatedwithhostingagridofVM's[Keaheyetal.2004].DestroyingavirtualclusterisassimpleassendingSIGKILLtoeachhypervisoranddeletingtheimagefromdisk.

KVMsupportsthestandardLinuxTUN/TAPmodelforEthernetbridging.Byusingthismodel,eachVMgetsitsownnetworkingresources,makingitindistin-guishablefromaphysicalmachine.

2.2VirtualComputeNodes

CentraltotheVirtualOrganizationClusterModel（VOCMistheVirtualOrgani-zationCluster（VOC,whichiscomposedofVirtualComputeNodes（VCN.EachVirtualOrganization（VOthatwishestoutilizethecomputefacilitiesprovidedbyaVirtualizationServiceProvider（VSPmustprovideaVMimageorsetofVMimages,alongwithsomegeneralcongurationparameters.SinceeachimagewillpotentiallybeusedtospawnmultipleVM's,thecongurationofeachimagemustnotmakeanyassumptionsaboutthetypeofnetworking（hardwareinterface,hostname,orsystem-speciccongurationsettings.Instead,dynamicnetworkingcongurationshouldbeused.Onceahostnamehasbeenobtained,dynamiccon-gurationbaseduponthehostnameisallowed.

OurmodelVOCwasbuiltfromtwoVCN's,eachwithCentOS5.1installed.CentOSprovidessubstantialout-of-the-boxsupportforclustercomputingappli-cationsand,alongwithitscousin,RedHatEnterpriseLinux,iswidelysupportedinthescienticandhigh-performancecomputingcommunities.ThetwoVCN'swere:

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（1Avirtualheadnode,whichwasconguredwiththeCondorcentralmanager

andsubmitdaemons（condor_collector,condor_negotiator,condor_schedd,Gangliamonitoringdaemon（gmond,andGangliametadaemon（gmetad.

（2Avirtualcomputeelement,whichwasconguredwiththeCondorjobstarter

（condor_startd,MPICH2,ATLAS（tunedforthevirtualCPU,andGangliamonitoringdaemon（gmond.

OurmodelVOCwasdesignedasanOpenScienceGrid（OSGcomputeelement.ThevirtualheadnodeusedCondortodistributeincomingOSGjobstothevirtualcomputeelements.

3.SUPPORTMODEL

Preparingthephysical（asopposedtovirtualclusterforVOCsupportrequiredconguringthehostOS,settingupsupportservices,conguringnetworkingser-vices,andconguringstorageservices.Inourprototypeimplementation,supportservicesincludedaLightweightDirectoryAccessProtocol（LDAPserverforcen-tralizedadministrationofhostsandphysicaluseraccounts,aDynamicHostCon-gurationProtocol（DHCPserverforassigningIPv4addressestonodes,andaDomainNameServer（DNSforhostresolution.

3.1HostOSconguration

Whenprovidingvirtualizationservices,thehostOSshouldbeminimalistinordertoreserveasmanyresourcesaspossiblefortheVCNs.Tothisend,SlackwareLinux12waschosenasthehostOS.AcustomkernelwascompiledtoenablesupportforKVMandadditionalnetworkmetrics.Allunnecessaryhardwaredriversandotherfeatureswereleftoutofthekerneltominimizeitsmemoryfootprint.KVMdrivermodulesalsowerebuiltforthecustomkernel.

Formaintainabilityreasons,alltheSlackwarenodeswereinstalledviaPXEbootandacustomautomatedinstallscript.Thisallowedthewholeclustertobere-createdquicklyincaseofaddednodes,hardwarefailure,oradministratorerror.AlladditionalsoftwarewasmaintainedintheformofSlackwarepackagestoallowforrapiddeploymentacrosstheentirecluster.

3.2PhysicalSupportServices

CongurationinformationforeachVCNwasstoredinanLDAPdatabasetopro-videacentralizedadministrationmechanism.EachVCNwasrepresentedasanLDAPentrywiththehostname,IPaddress,andMACaddresselds.TheMACaddresswasgeneratedasalocally-administeredaddressastoavoidconictswithanyotherMAC'sonthenetwork.AnLDAP-aware,batch,remoteadministrationtool