Both private networks fail. 

Node A races for majority of coordinator disks. 

If Node A wins race for coordinator disks, Node A ejects Node B from the shared disks and continues. 

Node B races for majority of coordinator disks. 

If Node B loses the race for the coordinator disks, Node B removes itself from the cluster. 

When Node B is ejected from cluster, repair the private networks before attempting to bring Node B back. 

Both private networks function again after event above. 

Node A continues to work. 

Node B has crashed. It cannot start the database since it is unable to write to the data disks. 

Restart Node B after private networks are restored. 

One private network fails. 

Node A prints message about an IOFENCE on the console but continues. 

Node B prints message about an IOFENCE on the console but continues. 

Repair private network. After network is repaired, both nodes automatically use it. 

Node A hangs. 

Node A is extremely busy for some reason or is in the kernel debugger. 

When Node A is no longer hung or in the kernel debugger, any queued writes to the data disks fail because Node A is ejected. When Node A receives message from GAB about being ejected, it removes itself from the cluster. 

Node B loses heartbeats with Node A, and races for a majority of coordinator disks. 

Node B wins race for coordinator disks and ejects Node A from shared data disks. 

Verify private networks function and restart Node A. 

Nodes A and B and private networks lose power. Coordinator and data disks retain power.  

Power returns to nodes and they restart, but private networks still have no power. 

Node A restarts and I/O fencing driver (vxfen) detects Node B is registered with coordinator disks. The driver does not see Node B listed as member of cluster because private networks are down. This causes the I/O fencing device driver to prevent Node A from joining the cluster. Node A console displays: 

Potentially a preexisting split brain. Dropping out of the cluster. Refer to the user documentation for steps required to clear preexisting split brain.

Node B restarts and I/O fencing driver (vxfen) detects Node A is registered with coordinator disks. The driver does not see Node A listed as member of cluster because private networks are down. This causes the I/O fencing device driver to prevent Node B from joining the cluster. Node B console displays: 

Potentially a preexisting split brain. Dropping out of the cluster. Refer to the user documentation for steps required to clear preexisting split brain.

Resolve preexisting split brain condition.  

See System panics to prevent potential data corruption 

Node A crashes while Node B is down. Node B comes up and Node A is still down. 

Node A is crashed. 

Node B restarts and detects Node A is registered with the coordinator disks. The driver does not see Node A listed as member of the cluster. The I/O fencing device driver prints message on console: 

Potentially a preexisting split brain. Dropping out of the cluster. Refer to the user documentation for steps required to clear preexisting split brain.

Resolve preexisting split brain condition.  

See System panics to prevent potential data corruption 

The disk array containing two of the three coordinator disks is powered off. 

Node B leaves the cluster and the disk array is still powered off. 

Node A continues to operate as long as no nodes leave the cluster. 

Node A races for a majority of coordinator disks. Node A fails because only one of three coordinator disks is available. Node A removes itself from the cluster. 

Node B continues to operate as long as no nodes leave the cluster. 

Node B leaves the cluster. 

Power on failed disk array and restart I/O fencing driver to enable Node A to register with all coordinator disks.