ITIL之可用性管理

ITIL之

可用性管理可用性管理郑重声明：仅限技术支持内部交流因参照本交流方法所引起的任何后果概不负责素材来源GuidingPrinciple#1-'AvailabilityisatthecoreofbusinessandUsersatisfaction'

'Agoodanalogyforexampleistoconsiderthepurchasingofanewcar.Cost,style,performanceandfeaturesareallimportant.However,ifthecarbreaksdownfrequentlythebuyerisunlikelyevertopurchaseanothercarfromthatmanufactureragain.GuidingPrinciple#2-'Recognisingthatwhenthingsgowrong,itisstillpossibletoachievebusinessandUsersatisfaction'GuidingPrinciple#3-'ImprovingAvailabilitycanonlybeginafterunderstandinghowtheITServicessupportthebusiness'

AvailabilityManagementneedstoconsiderAvailabilityfromanITServiceperspectiveandfromanITcomponentperspective.Theseareentirelydifferentaspects.Whiletheunderlyingconceptissimilar,themeasurement,focusandimpactareentirelydifferentthatfurtherimprovementstotheend-to-endservicewerealsoachievedbybusinessprocessimprovements,e.g.cashreplenishmentproceduresTheAvailabilityManagementProcessTheCostofAvailabilityKEYMESSAGE

'ImprovinglevelsofAvailabilitycanoftenbeachievedbyasmallstepChangeinthinkingratherthanalargestepchangeintechnology'.

TheCostofUnAvailabilityTheoptimumbalancetostrikebeingthecostoftheAvailabilitysolutionweighedagainstthecostsofUnAvailability.ThemonetaryimpactTangiblecostslostUserproductivitylostITstaffproductivitylostrevenueovertimepaymentswastedgoodsandmaterialimposedfinesorpenalties.IntangiblecostslossofCustomergoodwill(Customerdissatisfaction)lossofCustomerslossofbusinessopportunity(tosell,gainnewCustomersetc)damagetobusinessreputationlossofconfidenceinITServiceprovider

damagetostaffmorale.AvailabilitymeasurementandreportingAvailabilitymeasuresshouldbeincorporatedintoSLAs,OLAsandanyUnderpinningcontracts.TheseshouldbereviewedregularlyatServiceLevelreviewmeetings.Famoussayingsandtruthsaboutmeasurements:

'Ifyoudon'tmeasureit,youcan'tmanageit'

'Ifyoudon'tmeasureit,youcan'timproveit'

'Ifyoudon'tmeasureit,youprobablydon'tcare'

'Ifyoucan'tinfluenceit,thendon'tmeasureit'AvailabilitymeasurementandreportingKEYMESSAGE

AvailabilityManagementneedstoconsiderAvailabilityfromanITServiceperspectiveandfromanITcomponentperspective.Theseareentirelydifferentaspects.Whiletheunderlyingconceptissimilar,themeasurement,focusandimpactareentirelydifferent.Availabilitymeasurementandreporting

ITAvailabilitymeasures-thetraditionalview

%Available

%Unavailable

Duration

Frequencyoffailure

Impactoffailure

Availabilitymeasurementandreporting

ITAvailabilitymeasures-thetraditionalview

Availabilitymeasurementandreporting

MeasuringUserAvailability

thefrequencyofdowntimethedurationofdowntimethescopeofimpact.ThemethodologyemployedtoreflectUserAvailabilitycouldconsidertwoapproaches:ImpactbyUserminuteslost.Impactbybusinesstransaction.Availabilitymeasurementandreporting

Businessdrivenmeasurementandreporting

EstablishingtheVBF〔vitalbusinessfunctions〕tomeasureIndustryview

EffectivemanagementrequirestheabilitytoviewAvailabilityfromtheperspectiveofthebusinessapplication'

Example

ATMservice

Q:-whatisthemajorconsequenceonyourbusinessorCustomersifthereisanITfailure?

Isit:

A1:TheconsequenceofITfailureimpactinganATMserviceisthatourATMmachinesareunavailable.

A2:TheconsequenceofITfailureimpactinganATMserviceisthatourCustomerscannotobtaincashfromourATMmachines.

Whilebotharecorrect,thevitalbusinessfunctionforanATMserviceistheabilitytodispensecashnotprovideanATM.ThemoremeaningfulandpowerfulMetrictomeasurethereforeistheobtainingofcash.Availabilitymeasurementandreporting

ITAvailabilityMetricsModel

AvailabilityManagementmethodsandtechniquesComponentFailureImpactanalysis(CFIA)FaultTreeAnalysis(FTA)CRAMMCalculatingAvailabilityCalculatingtheCostofUnAvailabilityDevelopingbasicITAvailabilitymeasurementandreportingDevelopingbusinessandUsermeasurementandreportingSystemsOutageAnalysis(SOA)TheIncident'Lifecycle'ContinuousimprovementmethodologyTechnicalObservationPost(TOP).AvailabilityManagementmethodsandtechniquesAvailabilityManagementmethodsandtechniques

ComponentFailureImpactAnalysis

BasicCFIAHavingdeterminedtheITInfrastructureconfigurationtobeassessed,thefirststepistocreateagridwithCIsononeaxisandtheITServiceswhichhaveaDependencyontheCIontheother.ThisinformationshouldbeavailablefromtheCMDB.AlternativelythiscanbebuiltusingdocumentedconfigurationchartsandSLAs.Thenextstepistoperformthefollowingprocedureateachintersectionpointinthegrid:leaveablankwhenafailureoftheCIdoesnotimpacttheserviceinanywayinsertan'X'whenthefailureoftheCIcausestheITServicetobeinoperativeinsertan'A'whenthereisanalternativeCItoprovidetheserviceinserta'B'whenthereisanalternativeCI,buttheservicehastoberecoveredfirst.AvailabilityManagementmethodsandtechniques

ComponentFailureImpactAnalysis

Havingbuiltthegrid,CIsthathavealargenumberofXsarecriticaltomanyservicesandcanresultinhighimpactshouldtheCIfail.Equally,ITServicesthathavehighcountsofXsarecomplexandarevulnerabletofailure.ThisbasicapproachtoCFIAcanprovidevaluableinformationinquicklyidentifyingsinglepointsoffailure,ITServicesatriskfromCIfailureandwhatalternativesareavailableshouldCIfail.AvailabilityManagementmethodsandtechniques

ComponentFailureImpactAnalysis

ThesameapproachcanbeusedforasingleITServicebymappingthecomponentCIsagainstthevitalBusinessfunctionsandUserssupportedbyeachcomponent,thusunderstandingtheimpactofacomponentfailureonthebusinessandUser.ConfigurationitemVBFEndUsersImpactedPowerAll1,000CentralcomputerAll1,000ApplicationsAll1,000Disk#1Payments50Disk#2Orders100UtilityAEnquiry25AvailabilityManagementmethodsandtechniques

AdvancedCFIA

ProbabilityofFailure-thiscanbebasedontheMeanTimeBetweenFailure(MTBF)informationifavailableoronthecurrentAvailabilitytrends.Thiscanbeexpressedasalow/medium/highindicatororasanumericrepresentation.RecoveryTime-thisistheestimatedrecoverytimetorecovertheCI.Thiscanbebasedonrecentrecoverytimings,recoveryinformationfromdisasterrecoverytestingorascheduledtestrecovery.Recoveryprocedures-thisistoverifythatuptodaterecoveryproceduresareavailablefortheCI.DeviceIndependence-wheresoftwareCIshaveDuplexfilestoprovideresiliencethisistoensurethatfileplacementshavebeenverifiedasbeingonseparatehardwarediskconfigurations.DependentIDs-thisistoshowanydependenciesbetweenCIs.IfoneCIistofail,theremaybeanimpactonotherCIs,e.g.ifthesecurityCIwastofail,theoperatingSystemmaypreventtapeprocessing.AvailabilityManagementmethodsandtechniques

FaultTreeAnalysisAvailabilityManagementmethodsandtechniques

FaultTreeAnalysisEssentiallyFTAdistinguishesthefollowingevents:Basicevents-terminalpointsforthefaulttree,e.g.powerfailure,operatorerror.Basiceventsarenotinvestigatedingreaterdepth.Ifbasiceventsareinvestigatedinfurtherdepth,theyautomaticallybecomeresultingevents.Resultingevents-intermediatenodesinthefaulttreeresultingfromacombinationofevents.ThetopmostpointinthefaulttreeisusuallyafailureoftheITService.Conditionalevents-eventsthatonlyoccurundercertainconditions,e.g.failureoftheair-conditioningequipmentonlyaffectstheITServiceifequipmenttemperatureexceedstheserviceablevalues.Triggerevents-eventsthattriggerotherevents,e.g.powerfailuredetectionequipmentcantriggerautomaticshutdownofITServices.Theseeventscanbecombinedusinglogicoperators,i.e.:AND-gate-theresultingeventonlyoccurswhenallinputeventsoccursimultaneouslyOR-gate-theresultingeventoccurswhenoneormoreoftheinputeventsoccursExclusiveOR-gate-theresultingeventoccurswhenoneandonlyoneoftheinputeventsoccursInhibitgate-theresultingeventonlyoccurswhentheinputconditionisnotmet.AvailabilityManagementmethodsandtechniques

CRAMM

allpossibleRisksandCountermeasureshavebeenidentifiedallVulnerabilitieshavebeenidentifiedandtheirlevelsaccuratelyassessedallThreatshavebeenidentifiedandtheirlevelsaccuratelyassessedallresultsareconsistentacrossthebroadspectrumoftheITInfrastructurereviewedallexpenditureonselectedCountermeasurescanbejustified.AvailabilityManagementmethodsandtechniques

CalculatingAvailability

BasicAvailabilitycalculationTodeterminethebasicAvailabilityofagivenITServiceorcomponentasanAvailabilitypercentage(%)thefollowingbasicformulacanbeused:

Where:-AST=AgreedservicetimeDT=ActualdowntimeduringagreedservicetimeAvailabilityManagementmethodsandtechniques

CalculatingAvailability

Example

A24x7ITServicerequiresaweekly2-hourplanneddowntimeperiodforapplicationmaintenance.Followingthecompletionoftheweeklymaintenanceanapplicationsoftwareerroroccurswhichresultsin3hoursofunplanneddowntime.

TheweeklyAvailabilityfortheITServiceinthisreportingperiodisthereforebasedonthefollowing:

TheASTshouldrecognisethattheplanned2hrweeklydowntimeisscheduled.

TheDTisthe3hrsofunplannedoutagefollowingtheapplicationmaintenance.

TheASTvalueistherefore24hrsx7days-2hrsplannedmaintenance=166hrs/week.

TheDTvalueisthereforethe3hrsunplanneddowntime.

TheAvailabilitycalculationis:-

A=166-3/166x100=98.78%

BasicAvailabilitycalculationAvailabilityManagementmethodsandtechniques

CalculatingAvailability

TotalInfrastructureAvailability--SerialConfigurationAvailabilityasviewedfromtheUserworkstationisthereforecalculatedas:Availability=Host*Network*Server*WorkstationCalculation=0.98*0.98*0.975*0.96=0.8989TotalInfrastructureAvailability=89.89%.AvailabilityManagementmethodsandtechniques

CalculatingAvailability

TotalInfrastructureAvailability--ParallelConfigurationThehostcomponentAvailabilitypercentageisnowrecalculatedasfollows:Availability=1-((1-0.98)*(1-0.98))=0.9996HostAvailability=99.96%.AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

CFIACFIAisusedtohelppredictandevaluatetheimpactonITAvailabilityarisingfromcomponentfailureswithintheITInfrastructuredesign.theCFIAmatrixusedduringthisactivitycanbeexpandedtoincludefieldsthatcanmapthenumberofUserssupportedbyeachcomponentThuswhenacomponentisunavailable,thenumberofUsersimpactedisunderstood.ThiscanenableAvailabilitycalculationstobebasedonthenumberofUsersimpactedand/oramountoflostUserprocessingtime:Advantages-aneasytouseapproachthatenablesimpacttobereadilyidentifiedatthecomponentlevel.Disadvantages-thenumberofUserworkstationsdoesnotnecessarilyequatetothenumberofUsersatanyonepointintime,e.g.lunchhours,staggeredshiftpatternsorweekdayvs.weekendperiods.IntheseinstancesasuggestionwouldbetobasethenumberofUserswithintheCFIAmatrixuponanaverageforUsersactivewithinselectedperiods.

AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

End-UserassessmentFororganisationsunabletojustifythecostsofmoreadvancedAvailabilitymeasurementtechniques,theuseofadaily'Userassessment'isasimpletechniquethatprovidesabusinessandUserviewofITAvailability.Initsbasicform,thisisanagreedsetofcriteriaagainstwhichthebusinesscanassessITAvailabilityandservicequalityinsupportoftheirbusinessoperation.EachdaythebusinessUserrepresentativeshouldbecontactedfortheirend-of-dayassessment,thiscouldbereportedasaGOODday,ACCEPTABLEdayorBADday.Thiscanberecordedandreportedusingthe'RAG'(Red,Amber,andGreen)method.Thisapproachcanbeexpandedtoenablemorespecificassessmentinformationtobegathered,e.g.thebusinesscanassessanumberofcategories,e.g.Availability,performance,recoverabilityandbeextendedtoincludeotherITServiceManagementfunctions,i.e.ServiceDesk:Advantage-lowcostandeffective.ProvidesthebusinessviewofITAvailabilityandservicequality.Disadvantages-requiresbusinesscommitment.Withoutaframeworkofassessmentcriteriamaybeopentosubjectiveopinion.Maynotprovidesufficientdetailedinformationtodrivecontinuousimprovementactivities.AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

End-UsersimulationtoolsSystemsManagementtoolswhichseektosimulateUseractivitycanbedeployedtoprovideend-to-endAvailabilityreporting(real-timeandoff-linereports).ThesetoolsexecutescriptstogeneratesampletransactionsandmonitorandreportonareassuchasAvailability,performance,throughputetc:Advantages-providereal-timeexceptionreportingandrangeofoff-linereports.Additionallyasaby-productcontinuallyverifytheend-to-endInfrastructureandprovideanimmediatepostChangeimplementationhealthcheck.Disadvantages-thecostofprocurementandneedtocustomisescriptstoreflecttheorganisation'sapplication(s).AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

CustomercomplaintsThecorrelationofCustomercomplaintsreceivedagainstspecificITfailurescanprovideanindicationoftrueCustomerimpactandfrustration:Advantages-lowcostandreflectsatruesenseofCustomerdissatisfaction.Disadvantages-noteveryCustomercomplainssonotatruereflectionofimpact.TimelagbetweenIncidentsandcomplaintsbeingreceiveddelaysanddilutesAvailabilityreporting.AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

CompensationclaimsandpenaltypaymentsForcertainbusinessesaconsequenceofITfailuremaybeclaimsforfinancialcompensationbyimpactedCustomers.Anexamplebeingforthelossofinterestduetodelayedormissedpayments.Thisisnotrestrictedtothefinancialservicessector,forexamplesomemotoristassistancecompaniespaycompensation(orapenalty)forfailingtomeetarequestforassistancewithinasettimeperiod:Advantages-providesagoodindicationonthecostoffailure.Disadvantages-notallCustomersmakeclaimsorexercisepenaltypayment.AgaintimelagbetweentheIncidentsandresultantclaims(oftenmonths)candelayanddiluteAvailabilityreporting.AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

CalculatingUserAvailability--End-Userimpact(absolute)AvailabilityManagementmethodsandtechniques

DevelopingbusinessandUsermeasurementandreporting

CalculatingUserAvailability--End-Userimpact(productivity)EU