Dual-system hot backup

Introduction

Whenaserverisdown,theotherserverinthetwocomputerscanautomaticallytakeoverthebusinessofthedownserver,soastoensurethatnomanualinterventionisrequired.Thesystemcancontinuetoprovideservices.

Classification

Inthedual-systemhotbackupapplication,therecanbethreeworkingmodesaccordingtothedifferentworkingmodesofthetwoservers,namely:master-slave,mutualbackup,andparallel.Thefollowingisabriefintroduction:themaster-slavemodeiscurrentlycommonlyreferredtoastheactive/standbymode,theactiveserverisinworkingstate,andthestandbyserverisinthemonitoringreadystate,theserverdataincludesdatabasedata,anditiswrittentotwoserversorshareddataatthesametimeDiskarraystoragesystemtoensureinstantdatasynchronization.Whentheactiveserverfails,thestandbymachineisactivatedthroughsoftwarediagnosisormanuallytoensurethattheapplicationiscompletelyrestoredtonormalinashorttime.

Dualmachinemutualbackupmode,thismethodrequireshigherperformanceoftheserver,andtheconfigurationisrelativelybetter.

Parallelmodeisalsocalledduplexmode,whichisgenerallyusedforlarge-scalenetworkapplications,suchasOracledatabaseRAC(OradeRealApplicationCluster).BothserversareactiveandprovidethesameserviceatthesametimetoensureTheoverallperformancealsorealizesloadbalancingandmutualbackup,whichrequirestheuseofdiskarraystoragetechnology.

Amongthesethreemodes,themaster-slavemodeisthemostcommonlyuseddual-systemhotbackuptechnologyforsmallandmedium-sizednetworks.Thefollowingdescribesthetechnicalimplementationofthismodeindetail.

Datainformationisthekeytotheprogressanddevelopmentoftoday'ssociety.Facedwithanincreasinglylargecomputernetwork,theuser'srequirementisthatthenetworkcanoperatereliably,atahighspeed,andstably.Atpresent,mostnetworkservicesadoptthemodeofcentralserver.Thehighreliabilityandhighavailabilityoftheserverarethekeytothesafeoperationofthenetwork.Oncetheserverfails,theserviceprovidedwillbeinterrupted,affectingnormalwork,andmaylosethekeyData,whichhasseriousconsequences.Howtoresumeuseassoonaspossibleandensuredatasecurityintheeventofafailurehasbecomeanincreasinglyprominentissue.Theserverdual-systemhotbackuptechnologyisaneffectivemeasuretosolvethereliabilityreductioncausedbysoftwareandhardwarefailures.Thistechnologyisrelativelymatureandrelativelylowincost.Ithastheadvantagesofsimpleinstallationandmaintenance,stabilityandreliability,andintuitivemonitoring.Ithasbeenobtainedinnetworksecurity.Widerangeofapplications.

Principle

Dualmachinehotbackuptechnologyisahighfault-tolerantapplicationschemecombiningsoftwareandhardware.Theprogramiscomposedoftwoserversystemsandanexternalshareddiskarraycabinet(ornot,butRAIDcardsareusedintherespectiveservers)andthecorrespondingdual-systemhotbackupsoftware.

Inthisfault-tolerantsolution,theoperatingsystemandapplicationsareinstalledonthelocalsystemdisksofthetwoservers,andthedataoftheentirenetworksystemiscentrallymanagedandbackedupthroughthediskarray.Centralizeddatamanagementistoreadandstorethedataofallsitesdirectlyfromthecentralstoragedevicethroughthedual-machinehotbackupsystem,andismanagedbyprofessionals,whichgreatlyprotectsthesecurityandconfidentialityofthedata.Theuser'sdataisstoredinanexternalshareddiskarray.Whenaserverfails,thestandbymachinetakestheinitiativetoreplacethehosttoensureuninterruptednetworkservices.

Thedual-systemhotbackupsystemadoptsthe"heartbeat"methodtoensuretheconnectionbetweenthemainsystemandthebackupsystem.Theso-called"heartbeat"meansthatthemasterandslavesystemssendcommunicationsignalsatacertaintimeintervaltoeachother,indicatingthecurrentoperatingstatusoftheirrespectivesystems.Oncethe"heartbeat"signalstopsindicatingthatthehostsystemhasfailed,orthebackupsystemcannotreceivethe"heartbeat"signalfromthehostsystem,thehighavailabilitymanagementsoftwareofthesystemconsidersthatthehostsystemhasfailed,thehoststopsworking,andtransferssystemresourcestothestandbysystem.Onthesystem,thebackupsystemwilltaketheplaceofthehosttoensuretheuninterruptedoperationofnetworkservices.

Inthedual-systemhotbackupsolution,therecanbethreedifferentworkingmodesaccordingtotheworkingmodeofthetwoservers,namely:dual-systemhot-backupmode,dual-systemmutualbackupmodeanddual-systemduplexmode.

Operationmethod

Therearetwowaystoimplementdual-systemhotbackup.Oneisthatthetwoserversuseasharedstoragedevice(usuallyashareddiskarrayorstorageareanetworkSAN).),thedual-systemhotbackupisrealizedbyinstallingthedual-systemsoftware,whichiscalledthesharingmode.Theothermethodisthatthereisnosharedstoragedevice,andthedataisstoredineachserveratthesametime,whichiscalledthesoftware-onlymethodorthesoftware-synchronizeddatamethod.Theimplementationbasedonstoragesharingisthemoststandardsolutionfordual-systemhotbackup.Inthemaster-slavemode,twoserversprovideexternalserviceswithavirtualIPaddress,andtheservicerequestissenttotheactiveserver.Atthesametime,thetwoserversdetecttheworkingstatusoftheotherserverthroughaheartbeatline.Oncethemainserverfails,thestandbyservermakesajudgmentbasedontheheartbeatdetection,completestheswitchinashortperiodoftime,takesoveralltheresourcesonthemainmachine,andbecomesthenewmainserver.Duetotheuseofsharedstoragedevices,thetwoserversactuallyusethesamedata,whichismanagedbydual-computerorclustersoftware.

Theheartbeatlineisthelinkbetweenthemainandstandbyservers.Theso-called"heartbeat"isanerrordetectionmechanism,whichmeansthatthemasterandslavesystemssendcommunicationsignalsatacertaintimeintervaltoeachother,andperiodicallycheckThestateofeachnode(includingthestateofthesystemandthestateoftheapplication).Ifthenumberofheartbeatsignalsnotreceivedcontinuouslyreachesacertainnumber,thedual-systemhotbackupsoftwareconsidersthatthecorrespondingsystemhasfailed,andperformsactive/standbyswitching.Traditionally,theheartbeatfaultdetectionusestheserialcommunicationmethod,buttheTCP/IP-basedmethodhasbeenwidelyused.Betweenthetwoservers,youcanuseadirectnetworkcable,oryoucanconnectthenetworkcardsusedforheartbeatdiagnosisbetweenthetwoserversthroughaswitch.

Thedual-systemhotbackuptechnologyneedstobeimplementedthroughdual-systemorclustersoftware.Thedual-computersoftwareadoptsastructureddesign,andgenerallyincludesthefollowingmodules:

(1)Themanagementmoduleofthedual-computerstatusisresponsiblefordetectingtheworkingstatusofthedual-computerandjudgingthefaultstatus.

(2)Theexecutionmoduleofthedual-machinefunctionisresponsibleforexecutingthedual-machineadjustmentandswitchingcommandsissuedbythemanagementmodule.

(3)Theclientconfigurationmanagementtoolofthedual-computersystem,throughwhichtheremoteconfiguration,managementandmaintenancefunctionsofthedual-computersystemcanberealized.

Theworkflowofthedual-computersoftwareisroughlyasfollows:Whenthesoftwareisstarted,theconfigurationfileofthedual-computersystemisfirstread,whichdescribesthenetworkinformation,hardwaredescriptionandtaskdefinitionofeachnodeinthedual-computersystem.parameter.Thecoreprogramofthesoftwarereorganizesthestateofthedual-computersystemaccordingtotheconfigurationinformation,andestablishestheinitialstateofthedual-computer.Aftertheinitialstateofthenodeisestablished,themanagementmoduleadjuststhedualmachinesandallocatesnetworkresourcesaccordingtothecurrentnetworkstatusinformation,sothatthemasternodeinthedualThekeyprocessofthemissionismonitoredtoensurethehealthofresourcesforexternalservices.Aftertheaboveresourcesareestablished,thedual-computersystementersanormaloperatingstate.

Whenthereisanodefailureinthesystem,thedual-systemmanagementmodulemakesthechoiceofwhethertoswitchthedual-systemsystemaccordingtothecurrentstateofthedual-systemandtheroleofthefailednodeinthedual-system.Whenthenodeisthemasterserver,thedual-computersystemwillautomaticallytransfertheresourcesandtasksbelongingtothenodetothestandbyservertoensurethenormaloperationofthenetwork.Ifthefaultynodeisthestandbyserver,afterthedual-serversoftwareraisesanalarm,thetasktransferwillbeblockeduntilthestandbyserverisrepairedandre-enterthedual-serversystem.Afterthemanagementmoduledetectsthatthefaultisrepaired,thecurrenttaskwillbeunlocked.Operation,thesystemre-entersthenormaloperatingstate.

Workingmode

Dual-systemhotstandbymode

Theactive/standbymodeiscommonlyreferredtoatpresent,theactiveserverisinworkingstate,andthestandbyserverisinmonitoringInthereadystate,serverdataincludingdatabasedataiswrittentotwoormoreserversatthesametime(usuallyeachserverusesaRAIDdiskarraycard)toensureinstantsynchronizationofdata.Whentheactiveserverfails,thestandbymachineisactivatedthroughsoftwarediagnosisormanuallytoensurethattheapplicationcanbefullyrestoredtonormaluseinashorttime.Atypicalapplicationisasecuritiesfundserveroramarketquotationserver.Thisisamodethatiscurrentlyusedmoreoften,butbecausetheotherserverhasbeeninabackupstateforalongtime,thereisacertainamountofwasteintermsofcomputingresources.

Dualmachinemutualbackupmode

Tworelativelyindependentapplicationsarerunningontwomachinesatthesametime,buteachissetasabackupmachine.Whenaserverfails,Anotherservercantakeovertheapplicationofthefailedserverinashortperiodoftime,therebyensuringthecontinuityoftheapplication,buttheperformancerequirementsoftheserverarerelativelyhigh.Theconfigurationisrelativelygood.

Duplexduplexmode

isthecurrentcluster(cluster:clusterincludestwotypes,oneisnetworkloadbalancing,theotherisservercluster.HereisduplexduplexThemodeisaformofnetworkloadbalancingcluster.),twoserversareactiveandrunthesameapplicationatthesametimetoensuretheoverallperformance,andalsoachieveloadbalancingandmutualbackup.TypicalproductsthatimplementthistypeofprogramincludeRACofforeignmanufacturerOracle,MoebiusforSQLServerofdomesticmanufacturerGreytrend.Needtousediskcabinetstoragetechnology(preferablySanmethod).WEBserversorFTPserversoftenusethismethod.

Summary

Theabovebrieflyanalyzedtheconceptandmethodoftheserverdual-systemhotbackuptechnology.Inpracticalapplications,thedual-systemmodecanbeexpandedandimprovedaccordingtothenetworkscaleorimportance.Forthemulti-machineclustermode,twoormoreserversformacluster,anddeployontheseserversaccordingtotheactualsituationoftheapplication,andsetthetakeoverstrategyflexibly.Forexample,oneservercanbeusedasabackupforallotherservers,andmultipletakeoverrelationshipscanalsobesetup.Inaddition,therearenewertechnologiesthathaveemerged,suchasfault-tolerantservertechnology,whichusesredundantmethodsforallhardwareintheservertoachievefaulttolerance,whichcanachieveautomaticdetection,automatictakeover,andautomaticrecovery.Itisakindofhotbackupthandual-systemhotbackup.Solutionswithhigherlevelsofavailabilityaresuitableforcriticalbusinessapplications.