Disaster Tolerance and Recovery in a Serviceguard Cluster

Understanding Types of Disaster Tolerant Clusters

"objective" can be set for the recovery point such that if data is updated for a period less than the objective, automated failover can occur and a package will start. If the time is longer than the objective, then the package will not start. In a Linux environment, this is a user configurable parameter: RPO_TARGET.

•Extended Distance Cluster disk reads may outperform CLX in normal operations. On the other hand, CLX data resynchronization and recovery performance are better than Extended Distance Cluster.

Continental Cluster

A continental cluster provides an alternative disaster tolerant solution in which distinct clusters can be separated by large distances, with wide area networking used between them. Continental cluster architecture is implemented using the Continentalclusters product, described fully in Chapter 2 of the Designing Disaster Tolerant HA Clusters Using Metrocluster and Continentalclusters user’s guide. This product is available only on HP-UX and not on Linux. The design is implemented with two distinct Serviceguard clusters that can be located in different geographic areas with the same or different subnet configuration. In this architecture, each cluster maintains its own quorum, so an arbitrator data center is not used for a continental cluster. A continental cluster can use any WAN connection through a TCP/IP protocol; however, due to data replication needs, high speed connections such as T1 or T3/E3 leased lines or switched lines may be required. See Figure 1-6.

NOTE

A continental cluster can also be built using multiple clusters that

 

communicate over shorter distances using a conventional LAN.

 

 

Chapter 1

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