Conclusions

In making a comparison of the high availability features of clustering and sprayer, the following aspects should be considered.

HACMP is a very complex product and needs to establish multiple connections between the two servers. These connections must be allowed by the firewall. If SSH is used for HACMP communication between the servers, we have the benefit of encryption and authentication. However, using SSH will cause some of the HACMP scripts to report errors in the cluster verification, which can be ignored. Configuration and troubleshooting of this solution is not an easy job and produces an environment that is not easy to understand. Therefore, the firewall administrator must have a good understanding of HACMP to keep this solution running.

Using the high availability function provided with LB is fairly simple. The Load Balancer executes shell scripts for startup and takeover events, which configure the cluster IP addresses either to the loopback device or to the network card, depending on the state of the system. These scripts can be customized for your environment and can include commands to start and stop application proxies and generate alerts for takeover events. Because LB only uses one TCP connection on a dedicated port for the heartbeat, and ping for testing network functionality, there are few changes on the firewall configuration, so setup is fairly easy.

Both software packages can test network connectivity to determine if a network card on the active firewall has failed or if there is a general network failure by pinging other systems on that network.

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