Arbitrator Node Configuration Rules
Although you can use one arbitrator, having two arbitrators provides greater flexibility in taking systems down for planned outages as well as providing better protection against multiple points of failure. Using two arbitrators:
•Provides local failover capability to applications running on the arbitrator.
•Protects against multiple points of failure (MPOF).
•Provides for planned downtime on a single system anywhere in the cluster.
If you use a single arbitrator system, special procedures must be followed during planned downtime to remain protected. Systems must be taken down in pairs, one from each of the data centers, so that the Serviceguard quorum is maintained after a node failure. If the arbitrator itself must be taken down, disaster recovery capability is at risk if one of the other systems fails.
Arbitrator systems can be used to perform important and useful work such as:
•Hosting
•Running monitoring and management tools such as IT/Operations or Network Node Manager
•Running backup applications such as Omniback
•Acting as application servers
Disk Array Data Replication Configuration Rules
Each disk array must be configured with redundant links for data replication. To prevent a single point of failure (SPOF), there must be at least two physical boards in each disk array for the data replication links. Each board usually has multiple ports. However, a redundant data replication link must be connected to a port on a different physical board from the board that has the primary data replication link.
For Continuous Access P9000 and XP, when using
Calculating a Cluster Quorum
When a cluster initially forms, all systems must be available to form the cluster (100% Quorum requirement).
A quorum is dynamic and is recomputed after each system failure. For instance, if you start out with an
Each time a cluster forms, there must be more than 50% quorum to reform the cluster. With Serviceguard a cluster lock disk or Quorum Server is used as the
Example Failover Scenarios with One Arbitrator
Taking a node
Designing a Disaster Recovery Architecture for use with Metrocluster Products | 29 |