Initial joining of systems to cluster membership
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Initial joining of systems to cluster membership

When the cluster initially boots, LLT determines which systems are sending heartbeat signals, and passes that information to GAB. GAB uses this information in the process of seeding the cluster membership.

Seeding a new cluster

Seeding insures a new cluster will start with an accurate membership count of the number of systems in the cluster. This prevents the possibility of one cluster splitting into multiple subclusters upon initial startup. A new cluster can be automatically seeded as follows:

• When the cluster initially boots, all systems in the cluster are unseeded.
• GAB checks the number of systems that have been declared to be members of the cluster in the /etc/gabtab file.

  The number of systems declared in the cluster is denoted as follows:

  /sbin/gabconfig -c -n#

  where the variable # is replaced with the number of systems in the cluster.

  Note   Symantec recommends that you replace # with the exact number of nodes in the cluster.

• When GAB on each system detects that the correct number of systems are running, based on the number declared in /etc/gabtab and input from LLT, it will seed.
• HAD will start on each seeded system. HAD will only run on a system that has seeded.

  HAD can provide the HA functionality only when GAB has seeded.

Manual seeding of a cluster

Seeding the cluster manually is appropriate when the number of cluster systems declared in /etc/gabtab is more than the number of systems that will join the cluster. This could occur if a system is down for maintenance when the cluster comes up.

Caution   It is not recommended to seed the cluster manually unless the administrator is aware of the risks and implications of the command.

Before manually seeding the cluster, check that systems that will join the cluster are able to send and receive heartbeats to each other. Confirm there is no possibility of a network partition condition in the cluster.

Before manually seeding the cluster, do the following:

• Check that systems that will join the cluster are able to send and receive heartbeats to each other.
• Confirm there is no possibility of a network partition condition in the cluster.

To manually seed the cluster, type the following command:

/sbin/gabconfig -c -x

Note there is no declaration of the number of systems in the cluster with a manual seed. This command will seed all systems in communication with the system where the command is run.

So, make sure not to run this command in more than one node in the cluster

See Seeding and I/O fencing.