Seeding a cluster using the GAB auto-seed parameter through I/O fencing
If some of the nodes are not up and running in a cluster, then GAB port does not come up to avoid any risks of preexisting split-brain. In such cases, you can manually seed GAB using the command gabconfig - x to bring the GAB port up.
See Manual seeding of a cluster.
However, if you have enabled I/O fencing in the cluster, then I/O fencing can handle any preexisting split-brain in the cluster. You can configure I/O fencing in such a way for GAB to automatically seed the cluster. The behavior is as follows:
If a number of nodes in a cluster are not up, GAB port (port a) still comes up in all the member-nodes in the cluster.
If the coordination points do not have keys from any non-member nodes, I/O fencing (GAB port b) also comes up.
This feature is disabled by default. You must configure the autoseed_gab_timeout parameter in the
/etc/vxfenmode file to enable the automatic seeding feature of GAB.
See About I/O fencing configuration files.
To enable GAB auto-seeding parameter of I/O fencing
To disable GAB auto-seeding parameter of I/O fencing