HP Serviceguard manual Arbitration in Disaster-Tolerant Clusters, Extended Distance Clusters

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Arbitration for Data Integrity in Serviceguard Clusters

Arbitration in Disaster-Tolerant Clusters

Arbitration in Disaster-Tolerant Clusters

Disaster-tolerant clusters are those which are intended to survive the loss of a data center that contains multiple resources. Examples are an extended distance cluster where nodes may be separated into different data centers on one site; metropolitan clusters, where the nodes are separated into equal-sized groups located a significant distance apart; and continental clusters, in which the geographically separate data centers provide a home for entirely separate clusters, complete with storage devices.

Extended Distance Clusters

In extended distance (campus) clusters, the nodes are divided into two separate data centers in different buildings, which can be as far as 100 km apart. A dual cluster lock disk may be used for arbitration, with the two lock disks located in the two different data centers. This affords protection against the loss of one of the data centers. If a quorum server is used, it must be in a different location from either of the two data centers, thus providing additional protection against data center loss. Similarly, if arbitrator nodes are used, they must be in a different location from the two data centers.

An extended distance cluster is no different from a standard Serviceguard cluster except that components are subdivided by data center. This means that groups of nodes are located in different buildings, and storage units with mirrored data are placed in separate facilities as well.

Metropolitan Clusters

Arbitration in a MetroCluster configuration has traditionally followed a different model than that of the single arbitrator device (originally this was a lock disk). Because a MetroCluster configuration contains two distinct data centers at some distance from one another, the main protection has been against a partition that separates the two data centers into equal-sized groups of nodes. A lock disk is not possible in this type of cluster, since metropolitan clusters use a specialized data replication method rather than LVM mirroring. Since LVM is not used

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Contents Manufacturing Part Number B3936-90078 July Arbitration For Data Integrity Serviceguard ClustersLegal Notices Arbitration for Data Integrity in Serviceguard Clusters Membership Cluster Membership ConceptsCluster Membership Concepts Split-Brain QuorumTie-Breaking No Arbitration-Multiple Paths To Arbitrate or Not to ArbitrateMultiple Heartbeat Failures Single Node Failure No Arbitration-Multiple MediaAdditional Multiple Paths with Different Media Multiple Paths with Different MediaNo Arbitration-Risks Cluster Startup How Serviceguard Uses ArbitrationStartup and Re-Formation Cluster Quorum and Cluster Locking Dynamic Cluster Re-FormationCluster Lock No Cluster Lock Lock Requirements Lock Disk Operation Use of a Lock Disk as the Cluster LockDual Cluster Lock Single Cluster LockUse of a Lock LUN as the Cluster Lock Lock LUN Operation Oot IrrorQuorum Server Operation Use of a Quorum Server as the Cluster LockRunning the Quorum Server Setting up the Quorum ServerQuorum Server Status and State Specifying a Quorum ServerViewing Quorum Server System Data Viewing Quorum Server Status and StateUse of Arbitrator Node Use of Arbitrator NodesExtended Distance Clusters Arbitration in Disaster-Tolerant ClustersMetropolitan Clusters Quorum Server Arbitrator NodesUse of Dual Lock Disks in Extended Distance Clusters Continental ClustersDisk area is not mirrored Arbitration for Data Integrity in Serviceguard Clusters Summary Arbitration Advantages Disadvantages ModeComparison of Different Arbitration Methods Arbitration for Data Integrity in Serviceguard Clusters Summary
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