dell_xenServer_reference_architecture_v1.1

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DELLDellTM | Cit rix XenServerDell Edit ionReference Architec ture

VIRTUALIZATION SOLUTIONS ENGINEERINGSeptember 2008


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THISWHITEPAPER ISFOR INFORMATIONALPURPOSESONLY,ANDMAYCONTAINTYPOGRAPHICALERRORSAND

TECHNICAL INACCURACIES.THECONTENT ISPROVIDEDAS IS,WITHOUTEXPRESSOR IMPLIEDWARRANTIESOF

ANYKIND.

Dell, the DELL logo, EqualLogic, OpenManage, PowerVault, and PowerEdge are trademarks of Dell Inc.; Xen,XenServer,XenCenterandXenMotionareeitherregisteredtrademarksortrademarksofCitrixInc.;IntelandXeon

area registeredtrademarksof IntelCorporation in theU.S.andothercountries;AMD isaregisteredtrademark

andOpteron isatrademarkofAdvancedMicroDevices Inc.;Microsoft,Windows,Windows Vista,andWindowsServerareeithertrademarksorregisteredtrademarksofMicrosoftCorporationintheUnitedStatesand/orothercountries.

Othertrademarksandtradenamesmaybeusedinthisdocumenttorefertoeithertheentitiesclaimingthemarks

andnamesortheirproducts.Delldisclaimsproprietaryinterestinthemarksandnamesofothers.

Copyright2008DellInc.Allrightsreserved.Reproductioninanymannerwhatsoeverwithouttheexpresswritten

permissionofDellInc.isstrictlyforbidden.Formoreinformation,contactDell.

Informationinthisdocumentissubjecttochangewithoutnotice.


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Table of Contents

EXECUTIVESUMMARY.................................................................................................................................. 5

INTRODUCTIONANDSCOPE......................................................................................................................... 5

XenServerDellEditionIntroduction............................................................................................................. 6

CitrixXenServerDellEditionFeatures...................................................................................................... 6

FactoryinstalledfromDell.................................................................................................................... 6

Integratedsystemsmanagementandmonitoring............................................................................... 6

XenServerLocalConsole....................................................................................................................... 6

Optimizedfootprintandcontrolledenvironment................................................................................ 6

Improvedreliability............................................................................................................................... 6

ImprovedXenServerupdates............................................................................................................... 6

Precertifiedandsupportedconfigurations......................................................................................... 6

Dell|CitrixXenServerReferenceArchitecture............................................................................................ 7

SmallConfiguration................................................................................................................................... 9

MediumConfiguration............................................................................................................................ 10

HardwareConsiderationsforXenServerEnvironments............................................................................. 11

References.................................................................................................................................................. 13


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EXECUTIVESUMMARYThisDellVirtualizationReferenceArchitecture(RA)whitepaperdescribesvalidatedarchitecturesfor

Dell|CitrixXenServerDellEditionvirtualinfrastructures.TheVirtualizationRAisintendedtoprovide

customerswithanexamplebasistoconsider,evaluate,andselecttheDellvirtualizationsolution

componentsthatbestfittheirrequirements. Thisdocumentisnotintendedtobeanexhaustivestudy

ofspecificarchitecturesforeveryenvironment. Foracompleteevaluationofyourdatacenters

virtualizationrequirements,pleasecontactyourDellSalesrepresentative.

INTRODUCTIONANDSCOPECustomersarefacedwithmanychoiceswhenplanningavirtualizationdeployment.Server,storage,and

softwareconfigurationscanvarydependingonworkloadandfeaturerequirements.Thispaperproposes

severalsamplevirtualizationarchitecturesbasedonDellsserverandstorageproducts. Architectures

aredivided intothreemaincategories:Small,Medium,andLarge. Thesecategoriesarebasedonthe

featuresandcapacityofeachproduct,aswellasthecomplexityoftheoverallarchitecture. TheSmall

architecture is designed with simplicity in mind and focuses on providing basic functionality with

minimalhardware. Itdoesnotenableadvancedvirtualizationfeatures.TheMediumconfiguration is

designed to meet the production requirements of small and medium businesses by providing

economical SAN solutions, enhanced virtualization features, and backup options. Finally, the Large

configuration is a fullfeature virtualization solution using redundancy,1tomanymanagement, high

availabilityandenterpriseclassserverandstorageproducts.Thegoalsofthedocumentareasfollows:

IntroducecustomerstotheDell|CitrixXenServersamplereferencearchitectures. Clarify,aid,andsimplifythedecisionmakingprocessforcustomers.

ThescopeofthisdocumentislimitedtoDell|CitrixXenServerDellEditionvirtualizationsolutionsonly.

ItdefinesarchitecturesusingDellservers,storage,andnetworkingcomponents.Smallerarchitectures

using free products are possible, but are not described here. Custom configurations for specific

customerengagementsmayhavethirdpartyhardwareorsoftwareandhenceareoutofscope.

Thisdocumentisastartingpointinthedesignofavirtualizationsolution. Dellprovidesseveral

resourcesforthecompletedesignanddeploymentofvirtualizationsolutions. Forfurtherinformation

pleasevisitwww.dell.com/citrixorwww.dell.com/virtualizationforthelatestupdatedversions.

Thedocumentisarrangedasfollows:Section2includestheintroductionanddetailsthescopeofthe

document;Section3describesDell|CitrixXenServerDellEditionfeature,Section4describestwo

referenceconfigurations,Section4describesgeneralsizingconsiderationsandSection5containsthe

referencelinks.


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XenServerDellEditionIntroductionWith the64bitopensourceXenhypervisorat its core,CitrixXenServerDellEdition isapowerful

virtualization solution that enables efficient resource consolidation, utilization,dynamic provisioning,

andintegratedsystemsmanagement.XenServerDellEditionhasasmallfootprintand isoptimizedto

runfroman internalflashstorage inDellPowerEdgeservers.DellandCitrixhavepartneredtobring

prequalifiedandvirtualizationreadyplatformsfortoday'sdynamicandgrowingdatacenters.

CitrixXenServerDellEditionFeatures

FactoryinstalledfromDell

CitrixXenServerDellEditionisfactoryinstalledfromDellonselectPowerEdgeservers.Thisreducesthe

installationanddeploymenttimerequiredandsimplifiesthedeploymentprocesstogetyour

infrastructurereadytouse.Withminimalconfiguration,theXenServerhostisavailabletorunvirtual

machines.

Integratedsystemsmanagementandmonitoring

CitrixXenServerDellEditioncomespreinstalledwithDellOpenManageServerAdministrator.This

enablessystemsmanagementrightoutoftheboxwithoutanyadditionalneedtoinstallanagentonthe

host.

XenServerLocalConsole

TheXenServerDellEditionincludesanewXenServerLocalConsoleuserinterfacetoenablelocaladministrationof

thehost.XenServerLocalConsoleenablesuserstoconfigureandviewhostspecificpropertiessuchas

managementnetworkconfiguration,localstorageforvirtualmachines,etc.XenCenter,thestandardMicrosoft

WindowsmanagementconsolefortheXenServer,isalsoavailable.

Optimizedfootprintandcontrolledenvironment

XenServerDellEditionisoptimizedforasmallerdiskfootprintandwritestoflashstorage.Themajorityofthe

XenServerDelleditionfilesystemisReadOnlyandthusprovidesatightercontrolovertheXenServeroperating

environment.TheXenServerDellEditionhostagentsoftwarehasbeensignificantlyoptimizedtominimizethe

numberofwritecyclestotheflashstorage.XenServerwritestoflashstorageonlywhensomethingimportanthas

changedandmustberecorded.Writeminimizationhelpsimprovethelifeoftheflashstorage.

Improvedreliability

RunningXenServerDellEditiononaserver'sinternalflashstorageprovidesimprovedreliabilityoverrunningon

traditionalharddisks.Flashstoragedoesnothavemovingpartsandismorereliablethanaharddisk.

ImprovedXenServerupdates

Toimprovereliabilityofsoftwareupgrades,theXenServerDellEditionimagecontainsaprimaryandsecondary

copyoftheXenServerfilesystem.Anytimeanupdateisapplied,thesecondarycopygetsupdatedleavingthe

primarycopyinaknowngoodstate.Thesecondarycopybecomestheprimaryafterasuccessfulupgrade.An

updatetotheXenServerhostcanbeappliedusingtheXenServerlocalconsoleorXenCenter.

Pre certifiedandsupportedconfigurations

CitrixXenServerDellEditioniscertifiedandfullysupportedbyDellforselectserverandstorageconfigurations.

BothDellandCitrixhaveworkedcloselytoprovidethehighestqualityproductanduserexperience


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Dell|CitrixXenServerReferenceArchitectureTheDell|CitrixXenServerreferencearchitecturerepresentsapossiblesamplesolutionthatprovidesa

customerwithoptionstoconsiderwhenmeetingtheirdatacenterrequirements. InDellsreference

architecture,DellserverandstoragearethefoundationonwhichCitrixXenServerinfrastructureisbuilt.

SpecificXenServerfeaturesshouldbechosenbasedonthedatacenterneeds. Oncechosen,thesekey

XenServerfeatureswilldrivehardwarerequirements. Therefore,thefeaturesareasimportanttothe

designanddecisionprocessasthetraditionalQoSdeliverables.

Twosampleconfigurations:SmallandMediumarelistedhere.Theseconfigurationsaregeneric

deploymentsbasedonsolutionsizeandcapabilityandareindependentofthetargetapplication. The

recommendationsfocusonhardwarecapacityandsoftwarefeatures;theydonotattempttoprescribea

particularservermodelorchipset,asthesepreferencesmayvarybasedoncustomerrequirements.

Thefollowingtabledescribessamplecomponentsforeachconfiguration.CitrixXenServerfeaturesare

listedbelowandenabledwithrecommendedDellserverandstorage. Theseareexamplesofbaseline

architecturesthatcanbebundledtogetherintoadatacentertosolvecustomerproblems.

Table1:HardwareandSoftwarefeaturesoftheBaselineConfiguration

Small Medium

Description Simpleentrylevel

configuration

Designedforsmall&medium

business

ServerConfiguration

Servers PE2900III,

PE1950III

PER805

PEM600

PEM605

PEM805

PEM905

PE2950III

PER805

PER900

PER905

CPU 2Sockets/DualCore 2Sockets/QuadCore


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MinimumNICports Two(twoLANonMotherboard

ports)

Fourtosix(TwotofourLAN

onMotherboardportsplus

additionaladdinifnecessary)

DRAC Optional Yes

LocalStorage 5x73GB/

5x146GB

2x73GB

Internalstorage

controller

PERC6/iorSAS6/iR

(RAID1,5)

PERC6/iorSAS6/iR

(RAID1,5)

StorageConfiguration

StorageFabric LocalorexternalSAS/SATA

storage

NetworkbasediSCSI

StorageArray LocalStorage,MD1000,

MD1120

MD3000

MD3000i,

PS5000E,PS5000X,

PS5000XV

BackupServer N/A PE2900

BackupSoftware N/A BackupExec11D

BackupDevice N/A PowerVault

TL4000

SoftwareConfiguration

CitrixXenServerDellExpressor

EnterpriseEdition

CitrixXenServerDell

EnterpriseEdition

XenMotionlive

migration

Yes* Yes


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HighAvailability Yes* Yes

ResourceQoS

Controls

Yes* Yes

Multiserver

management

Yes* Yes

Resourcepools Yes* Yes

SharedIPbased

storage

Yes* Yes

VLANconfirmation Yes* Yes

DellEqualLogic

StorageAdapterYes Yes

Management

XenCenter Yes Yes

ITA Optional Yes

OpenManage

Administrator

Yes Yes

*FeatureisavailableonlyinCitrixXenServerDellEdition

SmallConfiguration

TheSmallconfigurationisdesignedtobeasimpleentrylevelconfiguration.EachserverisrunningCitrix

XenServerDellExpressorEnterpriseEdition. Thestoragerequirementsareexpectedtobelowsolocal

storagemaybesuitableforsomedeployments. Butdirectattachoptionsarealsoavailablewiththe

MD1000,MD1120,orMD3000.

Figure1belowisasampleinstanceofasmallconfigurationanddoesnotreflectallpossiblesmall

configurations. Itprovidesahighlevelviewofasmallconfiguration;butitalsohighlightsthatsomekey

XenServerfeaturesarenotconfigurablewithintheconstructofasmallconfiguration. Therefore,there

isaneedtoabstracthigherorderconfigurationssuchastheMediumandLargeconfigurations. Inthis

example,CitrixXenServerDellEditionisdeployedontwoPowerEdge2900IIIserversthatareattached

toaPowerVaultMD3000array.UsingMD3000array,thetwoXenServerhostscanshareastorageLUN,

thusenablinglivemigrationorXenMotionofvirtualmachineacrosstwohosts.PowerVaultMD3000

providesanidealenvironmentforsmallusewherehostscalabilityisnotabigconcern.PowerVault

MD3000providesupto15TBofrawdiskcapacityusing15SASorSATAdrives.UptotwoPowerVault


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MD1000diskenclosures,eachenclosureprovidingamaximumof15TBofrawstoragecanbedaisy

chainedtoPowerVaultMD3000toincreaserawstoragecapacitytoatotalof45TB.UsingSASHBAson

XenServerhostsanddualcontrollersonMD3000providesredundancyagainstanHBA,controllerorSAS

interconnectfailure.

AsabestpracticeitisrecommendedtosegregateXenServerhostmanagementtrafficfromother

managementtrafficsuchasstoragemanagement.NotethatinXenServer,themanagementnetwork

interfaceisusedforXenMotionorlivemigrationtraffic.Trafficsegregationcanbeachievedbyusing

separatephysicalswitchesorusingseparateVLANs.Asshowninthefigure,highavailabilityandload

balancingforvirtualmachinetrafficcanbeachievedbybondingtwoNICsoneachXenServerhost.

Figure1:AsamplesmallconfigurationforCitrixXenServerDellEdition

MediumConfiguration

TheMediumconfigurationistargetedtowardssmallandmediumbusinesscustomerstoenableboth

hostandstoragescalabilitythatismorethanwhatisofferedbythesmallconfiguration.Each

PowerEdgeserverrunningCitrixXenServerDellEnterpriseEditionenablescustomerstouseadvanced

featuressuchasresourcepools,integratedHA,XenMotion,andresourceQoS.

Figure2belowisasampleinstanceofamediumconfigurationanddoesnotreflectallpossiblemedium

configurations.CitrixXenServerDellEditionrunsonDellPowerEdgeR805servers,configuredina

resourcepool. AllXenServerhostsareconnectedviaanEthernetfabricandsharestorageontheDell

EqualLogicPS5000array(s). TwoNICsoneachhostareconfiguredasabondtoprovidehighavailability

foriSCSIstoragetraffic.TheiSCSItrafficisisolatedfromothernetworktrafficusingseparatephysical

Ethernetswitches.TwoNICsoneachhostarebondedtoprovidehighavailabilityandloadbalancingfor

virtualmachinetraffic.TwoNICsoneachhostarebondedtoprovidehighavailabilityandloadbalancing

forthehostmanagementandXenMotiontraffic.Thisconfigurationillustratestrafficsegregationusing


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separatephysicalswitches;howeverisolationcanalsobeachievedusingVLANs.XenCentercanbe

installedonanyworkstationorservermachinethathasaccesstothehostmanagementnetwork.

Figure2: AsamplemediumconfigurationforCitrixXenServerDellEdition

Upto16hostscanbeconfiguredaspartofasingleresourcepool.Beingpartofaresourcepoolallows

XenServerhoststoshareiSCSIstorageonPSSeriesarrays.Sharedstorageisarequirementforlive

migrationorXenMotionofvirtualmachine,providinguninterruptedVMmigrationfromonephysical

hosttoanother.UsingsharedstoragealsoallowsuserstoconfiguretheXenServerpoolforHigh

Availability,anewfeatureavailableinXenServer5.0.Dependingonthepoolconfigurationandrestart

priorityofVMs,incaseofahostfailure,XenServerHAfeaturerestartsvirtualmachinesonremaining

healthyhostsinthepool.

XenServer5.0alsointroducesadirectstorageadapterforDellEqualLogicPSSeriesarrays.Usingdirect

storageadapterforPSSeries,storagemanagementtasksforvirtualmachinescanbeachieveddirectly

usingXenCenterinterface.ThestorageadapteralsoenablesadvancedPSseriesfeaturessuchascloning

toinstantaneouslydeploynewvirtualmachines,virtualmachinessnapshots,thinprovisioning,etc.

HardwareConsiderationsforXenServerEnvironments

Thissectionprovidesgeneralscalingconsiderationsforhardwarewhendesigningavirtualized

infrastructure. Theguidancefocusesaroundthefourmajorhardwaresubsystems:(1)CPU;(2)memory;

(3)disk;and(4)network. Thesefoursubsystemsareimportanttounderstandinthegeneralsense

becausenotplanningforthemcanleadtopoorqualityofservice(QoS)inthedatacenter.

TheCPUsubsystemisakeycomponentindeliveringacceptableQoSinthedatacenter. Thedecision

hingesonchoosingtherightnumberofprocessorsandprocessortype.Inaddition,choosingbetween


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dualcoreprocessorsandquadcoreprocessorsinvolvemanyfactorssuchascostandperformance.

Ultimately,theserverneedsenoughphysicalCPUresourcestomeettheneedsofthevirtualized

infrastructureandtheneartermgrowth. Inshort,improvingCPUperformancecanbeaccomplishedby

choosingserverswithmoreprocessorcapacity,pickingprocessorswithhigherfrequencybinsor

upgradingtoquadcoreprocessorsfromdualcoreprocessors.

WhensizingCPUrequirementsforXenServer,itisfairtoassumethatoneprocessorcorewillbeusedby

theXenServerplatformwhiletheremainingavailableforusebythevirtualmachines.Thecontrol

domainisallocatedoneCPUandhenceusesoneoftheavailablecoresinthehost.XenServerDell

Editionsupportsupto8virtualCPUsperVM,howevertheguestOSmaysupportadifferentnumber.It

isrecommendedtoconfigureavirtualmachineisonevirtualCPUandaddmorevirtualCPUsif

necessary.

ThememorysubsystemisanotherimportantcomponentindeliveringQoSinthedatacenter. Themain

decisionistochoosetherightamountofmemorytomeettheneedsofthedatacenterandbalanceit

againstthecostofmemoryandthecostofaddingadditionalsystems. Next,thememoryneedisdriven

bythenumberofvirtualmachines,theamountofmemoryneededbyeachvirtualmachine,theamount

ofmemoryneededbythehypervisortomanagethoseVMs,andthememorycushionformigration

considerations. Sincememorytendstobethefirstresourcetobecompletelyutilized,carefulplanning

willensureenoughcapacitytosustainandgrowthedatacenter.

InXenServer,outofthetotalphysicalmemoryavailableonthehost,aVMisallocatedthefullchunkof

configuredmemory.HencewhenplannedmemoryrequirementsforXenServerhost,aggregatememory

requirementsforallVMsshouldbetakenintoconsideration.MemoryconsumedbyXenServerplatform

(Xenhypervisorandcontroldomain)varieswiththetotalphysicalmemoryavailableintheserver.The

Xenhypervisoruses128MBofmemoryregardlessofthephysicalmemoryontheserver.Thememory

usedbythecontroldomainisalwaysatleast200MB,andisnevermorethan752MB;withinthatrange

itisscaledasalinearfunctionoftotalhostRAM.Forhostswithupto3.5GBofphysicalRAM,thecontrol

domainusageremainsat200MB;ona5GBhostthecontroldomainwilluse228MB;ona16GBhostthe

controldomainconsumes454MB;andonhostswith32GBormorethecontroldomainconsumes

752MB.Therefore,thetotalmemoryusedbyXenServerplatformrangesanywherebetween328MBto

880MB.

ThedisksubsystemneedstoprovideenoughstoragecapacitywhiledeliveringQoStothedatacenter

throughacceptableIOrequestresponsetimes. Inaddition,thenumberofhostsconnectingtothedisk

subsystemandthefabrictypeneedtobefactoredinordertopickthecorrectDellstorageenclosure.

ThecapacityportionisasimplecalculationbasedonRAIDlevelchoiceandcapacityneedsforvirtual

machinesandapplications. Theseconddesigncriteriainvolveperformancesizingthedisksubsystem

andprovidingenoughdiskspindlesandbandwidthtohandletheIOneed.Toprovidebetterserviceto

I/Ohungryvirtualmachines,XenServerDellEnterpriseEditionallowsonetospecifyvirtualdiskI/O

priorityforvirtualdiskonLVMbasedstoragerepositories.


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ThenetworksubsystemneedstodeliverQoSonIOrequests,connectthedatacenter,andenablekey

hypervisorfeatures. ThedecisionpointsinvolvechoosingenoughNICportstohandletheVMdata

traffic,managementtraffic,andstoragetraffic(ifany)andbuildingasolidfabricinfrastructuretomeet

currentneedsandallowforscalabilityasthedatacentergrows.

XenServerDellEditionsupportsupto6activephysicalnetworkinterfaces(orupto6pairsofbonded

networkinterfaces)perXenServerhostandupto7virtualnetworkinterfacesperVM.XenServer5.0

introducesactive/activeNICbondingthatenablesloadbalancingandfailoverforvirtualmachinetraffic

andfailoverforothertypesofnetworktraffic.ForfinergraincontrolovernetworkbandwidthQualityof

Service,I/Oprioritycanbeset(XenServerDellEnterpriseEditiononly)foravirtualmachinesnetwork

interfacetolimitthetransferratetodesiredkilobytespersecond. ForIPstorage,asabestpracticeitis

recommendedtouseahighlyavailablenetworkinfrastructure:hostNICportsconfiguredasabond,

redundantswitchesandstoragearraywithredundantnetworkports/controllers.Adedicatedprivate

networkforIPstorageisrecommendedtoisolatestoragetrafficfromvirtualmachineandhost

managementtraffic.

References

CitrixXenServerDellEditionSolutionGuide:http://support.dell.com/support/edocs/software/Citrix/

Dell|CitrixSolutions:www.dell.com/citrix DellVirtualizationSolutions:www.dell.com/virtualization XenServerDellEditionProductDownloads:www.citrix.com/xenserver/dell DellPowerVaultStorage:www.dell.com/powervault DellEqualLogicStorage:www.dell.com/psseries

Trademarksusedinthistext:Dell,theDELLlogo,EqualLogic,OpenManage,PowerVault,andPowerEdgearetrademarksofDellInc.;Xen,XenServer,XenCenterandXenMotionareeitherregisteredtrademarksortrademarksofCitrixInc.;IntelandXeonare

aregisteredtrademarksofIntelCorporation intheU.S.andothercountries;AMD isaregisteredtrademarkandOpteron isa

trademarkofAdvancedMicroDevicesInc.;Microsoft,Windows,WindowsVista,andWindowsServerareeithertrademarksorregisteredtrademarksofMicrosoftCorporationintheUnitedStatesand/orothercountries.Othertrademarksandtradenamesmaybeusedinthisdocumenttorefertoeithertheentitiesclaimingthemarksandnames

ortheirproducts.DellInc.disclaimsanyproprietaryinterestintrademarksandtradenamesotherthanitsown.

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