When split brain occurs, not all nodes can communicate, so individual nodes or subsets of nodes might try to form individual or subset clusters. Each subset or partition might “believe” it has sole access and ownership to the multihost disks. Attempts by multiple nodes to write to the disks can result in data corruption.
If a node loses connectivity with other nodes, the node attempts to form a cluster with the nodes with which communication is possible. If that set of nodes does not form a quorum, Sun Cluster software halts the node and “fences” the node from the disks. Thus, Sun Cluster software prevents the node from accessing the disks. Only current member nodes have access to the disks, ensuring data integrity.
You can turn off fencing for selected disks or for all disks.
If you turn off fencing under the wrong circumstances, your data can be vulnerable to corruption during application failover. Examine this data corruption possibility carefully when you are considering turning off fencing. If your shared storage device does not support the SCSI protocol, such as a Serial Advanced Technology Attachment (SATA) disk, or if you want to allow access to the cluster's storage from hosts outside the cluster, turn off fencing.