What are the differences between failover modes on.doc
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What are the differences between failover modes on.doc

WhatarethedifferencesbetweenfailovermodesonaCLARiiONarray.doc

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"WhatarethedifferencesbetweenfailovermodesonaCLARiiONarray?"ID:emc157830Usage:37DateCreated:03/28/2007LastModified:01/07/2009STATUS:ApprovedAudience:CustomerKnowledgebaseSolutionQuestion:WhatarethedifferencesbetweenfailovermodesonaCLARiiONarray?Question:HowdohostsinteractwithdifferentfailovermodesonaCLARiiONarray?Question:WhathappenswhenchangingthefailovermodeonaCLARiiONarray?Question:HowdoeshostfailoversoftwarereacttodifferentCLARiiONfailovermodes?Environment:Product:CLARiiONCX-seriesEnvironment:Product:CLARiiONCX3-seriesEnvironment:Product:CLARiiONFC-seriesEnvironment:OS:OpenSystemsRootCause:ACLARiiONarrayisanActive/PassivedeviceandusesaLUNownershipmodel.Inotherwords,whenaLUNisboundithasadefaultowner,eitherSP-AorSP-B.I/OrequeststravelingtoaportSP-AcanonlyreachLUNsownedbySP-AandI/OrequeststravelingtoaportonSP-BcanonlyreachLUNsownedSP-B.ItisnecessarytohavedifferentfailovermethodsbecauseincertainsituationsahostwillneedtoaccessaLUNonthenon-owningSP.Fix:Thefollowingfailovermodesapply:FailoverMode0–LUNBasedTrespassModeThisfailovermodeisthedefaultandworksinconjunctionwiththeAuto-trespassfeature.Auto-trespassisamodeofoperationthatissetonaLUNbyLUNbasis.IfAuto-TrespassisenabledontheLUN,thenon-owningSPwillreportthattheLUNexistsandisavailableforaccess.TheLUNwilltrespasstotheSPwheretheI/Orequestissent.EverytimetheLUNistrespassedaUnitAttentionmessageisrecorded.IfAuto-trespassisdisabled,thenon-owningSPwillreportthattheLUNexistsbutitisnotavailableforaccess.IfanI/Orequestissenttothenon-owningSP,itisrejectedandtheLUN’sownershipwillnotchange.Note:ThecombinationofFailoverMode0andAuto-TrespasscanbedangerousifthehostissendingI/OrequeststobothSP-AandSP-BbecausetheLUNwillneedtotrespasstofulfilleachrequest.ThiscombinationismostcommonlyseenonanHP-UXserverusingPV-Links.TheAuto-trespassfeatureisenabledthroughtheInitiatorTypesettingofHP-AutoTrespass.AhostwithnofailoversoftwareshouldusethecombinationofFailoverMode0andAuto-trespassdisabled.FailoverMode1–PassiveNotReadyModeInthismodeofoperat