Meaning
Incommunicationengineering,redundancyreferstotheconsiderationofsystemsafetyandreliability,artificiallyreconfiguringsomekeycomponentsorfunctions.Whenthesystemfails,forexample,acertaindeviceisdamaged,theredundantlyconfiguredcomponentscanbeusedasbackuptointerveneintimeandundertaketheworkofthefailedcomponent,therebyreducingthefailuretimeofthesystem.Redundancyisespeciallyusedforemergencytreatment.Redundancycanexistatdifferentlevels,suchasnetworkredundancy,serverredundancy,diskredundancy,dataredundancy,andsoon.
Form
2.1Hardwareredundancy
Example:
1)Powerredundancy:High-endserverproductsgenerallyusedualpowersystems,Thesetwopowersourcesareloadbalanced,thatis,theyprovidepowertothesystematthesametimewhenthesystemisworking.Whenonepowersourcefails,theotherpowersourcewillimmediatelybearalltheload.SomeserversystemshaverealizedtheredundancyofDCpowersupplies,whileotherserverproductshaverealizedthefullredundancyofDCandACpowersupplies.
2)Storagesubsystem:Thestoragesubsystemisthemostpronetofailureintheentireserversystem.Redundancycanbeachievedthroughthefollowingmethods:
Diskmirroring:Writethesamedatatotwodisksseparately.
Diskduplex:AddanI/Ocontrollertothemirroreddisktoformadiskduplex,whichimprovesthebuscontention.
RAID(RedundantArraysofIndependent/InexpensiveDisks)iscomposedofmorethantwodisks,andasingledatastreamismadeinsequencethroughacontrollercoordinatedmotionmechanismInthesedisks,thereareRAID10,RAID01,RAID0,RAID5andotherlevels.
3)I/Ocardredundancy:NICredundancyreferstoinsertingmultipleNICsintheserver.Redundantnetworkcardtechnologywasoriginallyatechnologyonmainframesandmedium-sizedcomputers,andisnowgraduallybeingownedbyPCservers.Multiplenetworkcardscansharenetworktrafficandhavefaulttolerance.
4)CPUredundancy:Themainprocessorinthesystemdoesnotoftenfail,butsymmetricmultiprocessor(SMP)allowsmultipleCPUstosharetheworktoprovideacertaindegreeoffaulttolerance.
2.2InformationRedundancy
Example:ErrorCheckingandCorrectionMethod
2.3SoftwareRedundancy
Example:DualComputerClusterSoftware,CodeRedundancy
Insufficient
Theoriginalintentionofredundantconfigurationistoenhancethereliabilityofthesystem,buttheredundantconfigurationwillmakethesystemmorecomplicated,whichmakesiteasytointroducenewTheproblem.