云计算平台虚拟机.docx
《云计算平台虚拟机.docx》由会员分享,可在线阅读,更多相关《云计算平台虚拟机.docx(7页珍藏版)》请在冰豆网上搜索。
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
ACMTransactionsonComputationalLogic,Vol.V,No.N,Month20YY,Pages10?
?
.
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.
ACMTransactionsonComputationalLogic,Vol.V,No.N,Month20YY.
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:
ACMTransactionsonComputationalLogic,Vol.V,No.N,Month20YY.
4·M.Fennetal.
(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