The topologies for standby operation are as shown below.
Information
The topologies for standby operation include hot-standby and cold-standby operation.
Hot-standby operation enables preliminary operation so that the operating state can be established immediately on the standby node. In hot-standby operation, the state of the cluster application running on the operating node will be Online, while that of the cluster application on the standby node will be Standby. To perform hot-standby operation, hot-standby must be supported by the PRIMECLUSTER product to be used, the ISV application, and the user applications.
Cold-standby operation does not allow the preliminary operation needed to establish the operating state immediately on the standby node. In cold-standby operation, the state of the cluster application on the operating node will be Online, while that of the standby node will be Offline.
Definition
It is an operation mode in which a cluster system consists of 2 nodes. One is operating, and the other is standby. When a failure occurs in the operating node, a cluster application switches to the standby node. This does not disrupt ongoing operation.
Advantage
This operation mode ensures the availability of the cluster application even after failover.
Note
Nodes in whole system cannot be used efficiently because of a redundant configuration.
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Definition
It is an operation mode in which a cluster system consists of 2 or more nodes. Normally, 2 nodes are used in this operation mode. Each node has one operating and one standby cluster applications. The operating cluster application has its own standby in each other's node.
Advantage
Since all the nodes are operating for cluster application, the nodes in whole system can be used efficiently.
Note
If failover occurs for any of the cluster applications, the performance of the cluster applications may drop because two or more cluster applications will be operating in the failover node. For this operation mode, you need to estimate adequate resources.
Failover image
Definition
It is an operation mode in which a cluster system consists of 3 or more nodes. One is standby, and the others are operating. When a failure occurs in one of the operating nodes, a cluster application switches to the standby node. If a failure occurs in two or more operating nodes at the same time, the cluster applications switch to the standby node.
Advantages
This operation mode ensures the availability of the cluster application even after failover.
Since one node serves as the STANDBY node for multiple cluster applications, the STANDBY cost can be reduced when the number of cluster applications is large.
Note
If failover occurs for multiple cluster applications, the performance of the cluster applications is reduced because multiple cluster applications will be operating in one node.
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Cascade (using one cluster application)
Definition
It is an operation mode in which a cluster system consists of 3 or more nodes: one is operating, and the others are standby. When a failure occurs in the operating node, a cluster application switches to one of the standby nodes. When a failover is even failed, this cluster application switches to other standby node.
Advantages
Even after one node is stopped, the redundant configuration of the cluster application can be maintained by using other nodes. The availability is guaranteed during system maintenance.
This operation mode ensures the availability of cluster applications even after failover.
Note
As the system has a redundant configuration, nodes in whole system cannot normally be used efficiently.
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In this example, the nodes are defined in the sequence Node 1, Node 2, and Node 3 starting from the node with the highest cluster application priority. These nodes are defined when the cluster application is set up.
See
For information on how to set the cluster application priority, see Step 4 in "6.7.2.1 Creating Standby Cluster Applications."
Priority transfer (application of N:1 standby)
Definition
One node functions as STANDBY for multiple cluster applications. For the other nodes, one cluster application functions as OPERATING for every node of the other nodes while the other multiple cluster applications function as STOP.
This topology uses the exclusivity function between cascade and cluster applications.
Advantages
On that node on which one cluster application is OPERATING, the other cluster applications do not become either OPERATING or STANDBY. Therefore, the throughput of that cluster application is guaranteed even after failover occurs.
Because failback of the cluster application is not necessary during the restoration of a cluster application, a job can also be continued during the restoration.
Since one node is used as STANDBY exclusively for multiple cluster applications, the cost incurred for standby can be saved when there are many cluster applications.
Notes
Since one node is used as STANDBY of multiple cluster applications, availability decreases when there are many cluster applications.
If a failover occurs due to the occurrence of an error on one node, the availability decreases because no standby node is available until the completion of the maintenance work.
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