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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 resource
3、Sample 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 d
4、ifferent 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 dat
5、a.,7,MNSScenario: 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, bu
6、t have a 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 s
7、peaking, a 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 resou
8、rce is how the 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
9、same file share online.,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
10、 quorum resource: arbitration (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
11、majority.,The cluster must 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 qu
12、orum resource: arbitration (5),14,MNSPurpose 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 resour
13、ce: storage,For storage, the cluster registry and 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 com
14、mitted if the cluster service can make the update on 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 appende
15、d with a $ to make it hidden. It is created under the SystemRoot, 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
16、 good use of MNS.,20,MNSDeployment of MNS (2),If the sites lose communication 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 offline until manual intervention from an administrator.,23,MNSDeployment of MNS (5),
