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Donald K. Burleson

Oracle RAC Tips

Failover Cluster Architecture

Normally, the failover cluster is implemented in two types of architectures. They are Active/Passive architectures and Active/Active architectures.

  • Active/Passive Clusters – This type comprises two nearly identical infrastructures, logically sitting side-by-side. One node hosts the database service or application, while the other rests idly, waiting in case the primary system goes down. They share a storage component, and the primary server gracefully turns over control of the storage to the other server or node when it fails. If failure of the primary node occurs, the inactive node becomes the primary and hosts the database or application.
  • Active/Active Clusters – In this type, one node is assigned as primary for the database instance and another one is assigned the secondary node for failover purposes. At the same time, the secondary node acts as primary for another instance and the original primary node acts as the backup/secondary node. Fig 3.9 shows an example of active/active architecture.

Fig 3.10 Two Node Cluster with Active/Active Resource groups

The Active/Passive architecture is the most widely used. Unfortunately, this option is usually capital intensive and expensive. But for simplicity and manageability, many administrators prefer this arrangement. Active/Active architecture is a better cost-benefit solution since the backup server is put to use. However, it can result in performance problems when database services (or applications) failover to a single node. As the surviving node picks up the load from the failed node, performance issues may arise.

For more information, see the book Oracle 11g Grid and Real Application Clusters 30% off if you buy it directly from Rampant TechPress . 

Written by top Oracle experts, this RAC book has a complete online code depot with ready to use RAC scripts.  


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