Advanced Failover Configurations

The advent of SANs, combined with second-generation high-availability (HA) products such as VCS, has enabled several new and useful failover configurations, described in the following sections.

N + 1 Configuration

With the capabilities introduced by storage area networks (SANs), you can not only create larger clusters, but more importantly, can connect multiple servers to the same storage.

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N+1 Configuration

A dedicated, redundant server is no longer required in the configuration. Instead of N-to-1 configurations, there is N+1. In advanced N+1 configurations, an extra server in the cluster is spare capacity only.

When a server fails, the application service group restarts on the spare. After the server is repaired, it becomes the spare. This configuration eliminates the need for a second application failure to fail back the service group to the primary system. Any server can provide redundancy to any other server.

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N+1 Failover