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1、1,Majority Node Set support in Microsoft WindowsServer2003 clustersSteve MathiasPremier ServicesMicrosoft Corporation,2,Objectives,This presentation will discuss a new feature of Microsoft Windows Server 2003 clusters named Majority Node Set(MNS).This presentation assumes a basic knowledge of server
2、 clustering(MSCS).,3,Agenda,What is MNS?MNS is designed for a handful of key scenarios:Clusters that have geographically dispersed cluster nodesClusters that do not require a“shared disk”Purpose of a quorum resource:ArbitrationStorage,4,Agenda(continued),Define how MNS behaves as a quorum resourceSa
3、mple deployment of a MNS server clusterDefine where MNS is configuredWhat to consider when using MNSBasic troubleshooting of the MNS resource,5,MNSWhat is MNS?,MNS is a new quorum-capable resource based on replicating data to local disks of a majority of cluster nodes.,6,MNSScenario:clusters in diff
4、erent geographic sites,MNS provides an alternative quorum resource for clusters that have nodes in separate geographic sites.Useful for clusters with physically separate storage subsystems that implement“mirroring”to replicate data.,Note:MNS is for quorum information and does not replicate data.,7,M
5、NSScenario:no shared disk required for the application,It is now possible to create a server cluster that does not have any shared disk for the quorum resource.Here are several reasons why this can be done:Applications can fail over and have configuration information stored on the cluster,but have a
6、 way of keeping data in sync with the other cluster nodes.Applications can fail over and store information on another server cluster with file shares,or to a NAS device.Application is read-only or does not change frequently.For testing purposes.,8,MNSPurpose of a quorum resource,Generally speaking,a
7、 quorum resource must provide two key functions:Arbitration,if the nodes of the cluster cannot communicate with each other.Storage,for cluster configuration to maintain consistency on all nodes of the cluster.,9,MNSPurpose of a quorum resource:arbitration,Arbitration of the quorum resource is how th
8、e cluster service prevents“split-brain.”In a split-brain scenario,network communication failures cause a cluster to break into disjoint partitions of nodes,and each partition wants to individually act as the cluster.Example of split-brain:Both nodes in a two-node cluster bring the same file share on
9、line.,10,MNSPurpose of a quorum resource:arbitration(2),The cluster service cannot prevent communication from breaking down,but the cluster service can declare that only the partition that successfully arbitrates for the quorum resource can act as the cluster.,11,MNSPurpose of a quorum resource:arbi
10、tration(3),With MNS as the quorum resource,the cluster service will only run if a“majority”of the configured nodes are running and communicating with each other.MNS solves the quorum arbitration problem because it is impossible for multiple disjoint partitions to contain a majority.,The cluster must
11、 have“quorum.”,12,MNSPurpose of a quorum resource:arbitration(4),To determine if we have a majority of nodes running,we use the following algorithm:(/2)+1Example with a seven-node cluster:7/2+1=4Four nodes must be online to have a majority.,13,MNSPurpose of a quorum resource:arbitration(5),14,MNSPur
12、pose of a quorum resource:arbitration(6),If there are fewer nodes,the cluster is said to not have a majority,and therefore the cluster service will not start.By default,the cluster service will try to restart indefinitely.,15,MNSPurpose of a quorum resource:storage,For storage,the cluster registry a
13、nd checkpoint files are stored on each local node,versus a“shared disk.”,16,MNSPurpose of a quorum resource:storage(2),Ensures that the cluster configuration(ClusDB)is the same on all nodes of the cluster.Change is only considered to have been committed if the cluster service can make the update on
14、a majority of the nodes.The majority is calculated by:(/2)+1,17,MNSPurpose of a quorum resource:storage(3),When you create a MNS-based cluster,each node will have a hidden file share.The name of the share will be the MNS resource GUID appended with a$to make it hidden.It is created under the SystemR
15、oot,in the Cluster folder.,%WINDIR%ClusterMNS.78c0268e-f2cf-434c-afe0-cf2a7742c968$,18,MNSPurpose of a quorum resource:storage(4),Quorum tab in cluster administrator,19,MNSDeployment of MNS,Creating a primary site and a backup site is a good use of MNS.,20,MNSDeployment of MNS(2),If the sites lose c
16、ommunication with each other,the backup site will go offline because it does not have“Quorum.”,21,MNSDeployment of MNS(3),If the backup site has a failure,the primary site will remain online.,22,MNSDeployment of MNS(4),If the primary site has a failure,both the primary and backup site will be offlin
17、e until manual intervention from an administrator.,23,MNSDeployment of MNS(5),The cluster service on the nodes in the backup site must be started with the ForceQuorum parameter.,24,MNSForceQuorum parameter,On all nodes in the backup site,start the cluster service with the list of all nodes that are
18、still available.Click the Start button to start the cluster service,not the OK button.,MNSForceQuorum switch,If the primary site is going to be down for a long time,you can create the ForceQuorum key in the registry.,26,MNSSetup,Configure MNS during cluster configuration by clicking the Quorum butto
19、n.,27,MNSConsiderations,Odd-number clusters are generally better than even-number clusters.Consider if you have a six-node cluster with three nodes at two different sites:If the site link breaks,a loss of three nodes will be experienced at each site.Both sites will shut down and will require manual
20、intervention to start either site.,28,MNSTroubleshooting,The cluster service depends on the server service for the quorum file share.Permissions on both the share and NTFS file system must be selected for local Administrators Full Control.RDR and SRV errors to the server service may prohibit cluster
21、 configuration updates.Map a drive to the hidden share of each node,and then try to copy a test file.,29,Additional resources,“Server Clusters:Majority Node Sets(a.k.a.Quorum of Nodes)”“Quorums in Microsoft Windows Server 2003 Clusters”“Geographically Dispersed Clusters in Windows Server 2003”,Thank
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