ASANVolumeControllernodeisasingle processingunit,whichprovides virtualization, cache,andcopyservicesfor theSAN.
Nodes aredeployedinpairscalledI/Ogroups.Onenodeintheclusteris
designated theconfigurationnodebuteach nodeintheclusterholdsacopyofthe clusterstate information.
Relatedconcepts
“Clusters”
Allconfigurationandserviceisperformedat theclusterlevel.
Relatedreference
“Nodes”onpage13
ASANVolumeControllernode isa singleprocessingunitwithina SANVolume Controllercluster.
Clusters
Allconfigurationandserviceisperformedattheclusterlevel.
Aclustercanconsistof twonodes,withamaximumofeight nodes.Therefore,you can assignupto eightSANVolumeControllernodestoonecluster.
Someservice actionscanbeperformedat nodelevel,butallconfigurationis replicatedacrossallnodesinthecluster. Becauseconfigurationisperformedatthe clusterlevel,anIPaddressisassignedtotheclusterinsteadof eachnode.
Allyourconfigurationandserviceactions areperformedat theclusterlevel.
Therefore,afterconfiguring yourcluster,youcantake advantageof the virtualization andtheadvancedfeaturesof theSANVolumeController.
Clusterstateandthe configurationnode
Theclusterstate holdsallconfigurationandinternalclusterdatafor thecluster. This clusterstate informationisheldinnonvolatilememory.If themainlinepowerfails, thetwouninterruptiblepowersuppliesmaintaintheinternalpowerlongenoughfor theclusterstate informationtobestoredontheinternaldiskdrive ofeach node.
Thereadandwritecacheinformationisalso heldinnonvolatilememory.Similarly,if thepowerfailstoanode, configurationandcachedatafor thatnodewillbelost andthepartner nodeattemptsto flushthecache.Theclusterstateisstill maintained bytheothernodesonthecluster.
Figure7onpage12showsanexampleclustercontaining fournodes.Thecluster state showninthegreyboxdoesnotactuallyexist,insteadeachnodeholdsa copy of theentireclusterstate.
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Theclustercontainsasinglenode thatiselected astheconfigurationnode.The configurationnodecan bethoughtof asthenodethatcontrols theupdating of cluster state.For example,a userrequestismade (item1),thatresultsinachange beingmadeto theconfiguration.Theconfigurationnodecontrolsupdates tothe cluster (item2).Theconfigurationnode thenforwardsthechangetoallnodes (includingNode1), andtheyallmakethestate-changeatthesamepointintime (item 3).Usingthis state-drivenmodelofclusteringensuresthatallnodesinthe cluster knowtheexactclusterstateat anyonetime.
Clusterconfigurationbackup:
Configurationbackup istheprocess ofextractingconfigurationdatafromacluster andwriting itto disk.
Backing uptheclusterconfigurationenablesyouto restoreit intheeventthat configurationdataislost.Thedatathatisbackedupisthemetadata thatdescribes theclusterconfiguration,notthedatathatyourenterpriseusestorunitsbusiness.
Thebackupconfigurationfilescanbesavedonthemasterconsoleorthe configurationnode.
Objectsincludedinthe backup
Configurationdata isinformationabout aclusterandtheobjectsthataredefinedin it.Thefollowingobjectsarecopied:
v Storagesubsystem v Hosts
v I/Ogroups
v Manageddisks(MDisks) v MDiskgroups
v Nodes
v Virtualdisks(VDisks) v VDisk-to-hostmappings v SSHkey
v FlashCopymappings
v FlashCopyconsistency groups v RemoteCopyrelationships v RemoteCopyconsistencygroups
Cluster
Cluster state
Node 1 Node 2 Node 3
Copy of cluster state Copy of
cluster state Copy of
cluster state Copy of
cluster state
Node 4 1
2
3 3 3 3
Configuration node
Figure7.Cluster,nodes,andclusterstate.
Relatedconcepts
“Clusters”onpage11
Allconfigurationandserviceisperformedat theclusterlevel.
“Configurationrestore”
Configurationrestoreistheprocessof usinga backupconfigurationfile,orfiles, onthemasterconsoleor configurationnode torestoreaspecificcluster
configuration.
Configuration restore:
Configurationrestoreistheprocessofusingabackup configurationfile, orfiles,on themasterconsoleor configurationnode torestoreaspecificclusterconfiguration.
Restoringyour clusterconfigurationinvolvesrestoring themetadata thatdescribes your clusterconfiguration,notthedatayourenterpriseusesto runitsbusiness.
Restoringyour clusterconfigurationisanimportantpartofa completebackup and disaster recoverysolution.However,youmust makeprovisionfor your
non-configurationdatato berestoredaswell.
This processconsistsof twophases:
v Preparing v Executing Restorephases
Beforeissuingthepreparationcommand,or phase,theclusteritselfmust bereset to adefaultstate withthecorrectclustername.Duringthepreparationphase,the backup dataandthenew clusterareanalyzedfor compatibility,anda sequenceof commands isprepared.
Duringtheexecutionphase,thecommandsequenceisrun.
Relatedconcepts
“Clusters”onpage11
Allconfigurationandserviceisperformedat theclusterlevel.
Chapter5, “Backingupandrestoring theclusterconfiguration,”onpage231 Youcanbackupandrestoretheclusterconfiguration.
“Clusterconfigurationbackup”onpage12
Configurationbackupistheprocessofextractingconfigurationdatafroma clusterandwritingitto disk.
Nodes
ASANVolumeControllernodeisasingle processingunitwithinaSANVolume Controllercluster.
For redundancy,nodesaredeployedinpairsto makeupacluster.Aclustercan have onetofourpairsof nodesinit.EachpairofnodesisknownasanI/Ogroup.
Each nodecanbeinonly oneI/Ogroup.Amaximumof fourI/Ogroupseach containing twonodesissupported.
At anyonetime,asinglenode intheclusterisusedto manageconfiguration activity.Thisconfigurationnodemanagesacacheoftheconfigurationinformation thatdescribestheclusterconfigurationandprovidesa focalpoint forconfiguration commands. Iftheconfigurationnodefails,anothernode intheclusterwilltakeover itsresponsibilities.
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Table5 describestheoperationalstatesof anode.
Table5.Nodestate
State Description
Adding Thenodewasaddedtotheclusterbutisnotyet synchronizedwiththeclusterstate(seeNote).
Deleting Thenodeisintheprocessofbeingdeletedfrom thecluster.
Online Thenodeisoperational,assignedtoacluster,and hasaccesstothefibre-channelSANfabric.
Offline Thenodeisnotoperational.Thenodewas assignedtoaclusterbutisnotavailableonthe fibre-channelSANfabric.RuntheDirected
MaintenanceProcedurestodeterminetheproblem.
Pending Thenodeistransitioningbetweenstatesand,ina fewseconds,willmovetooneoftheotherstates.
Note: ItispossiblethatanodecanstayintheAddingstateforalongtime.Ifthisisthe case,deletethenodeandthenre-addit.However,youshouldwaitforatleast30minutes beforedoingthis.Ifthenodethathasbeenaddedisatalowercodelevelthantherestof thecluster,thenodewillbeupgradedtotheclustercodelevel,whichcantakeupto20 minutes.Duringthistimethenodewillbeshownasadding.
Relatedconcepts
“Configurationnode”
Atanygiventime,onenodemanagesconfigurationactivity.Thisnode isthe configurationnode.
Configuration node:
At anygiventime, onenodemanagesconfigurationactivity.Thisnodeisthe configurationnode.
Theconfigurationnodeisafocalpointfor configurationcommands, anditmanages thedatathatdescribestheclusterconfiguration.
If theconfigurationnodefails,theclusterchoosesanew configurationnode.This actioniscalledconfigurationnodefailover.Theswitchthatcontainsthenew node takesovertheclusterIPaddress.Thusyoucan accesstheclusterthroughthe sameIPaddressalthough theoriginal configurationnodehas failed.During the failover,thereisashortperiodwhenyoucannotusethecommandline toolsor SANVolumeControllerConsole.
Thefigure belowshowsanexampleclustercontaining fournodes.Node1has been designatedtheconfigurationnode. Userrequests (1)aretargetedatNode1.
This mayresultinrequests (2)beingtargetedat theothernodesinthecluster,and data beingreturnedtoNode1. SeeFigure8onpage15formoreinformation.
Relatedreference
“Nodes”onpage13
ASANVolumeControllernode isa singleprocessingunitwithina SANVolume Controllercluster.