About I/O fencing

I/O fencing protects the data on shared disks when nodes in a cluster detect a change in the cluster membership that indicates a split-brain condition.

The fencing operation determines the following:

This decision prevents possible data corruption. The installer installs the I/O fencing driver, part of VRTSvxfen RPM, when you install Veritas InfoScale Enterprise. To protect data on shared disks, you must configure I/O fencing after you install Veritas InfoScale Enterprise and configure SFCFSHA.

I/O fencing modes - disk-based and server-based I/O fencing - use coordination points for arbitration in the event of a network partition. Whereas, majority-based I/O fencing mode does not use coordination points for arbitration. With majority-based I/O fencing you may experience loss of high availability in some cases. You can configure disk-based, server-based, or majority-based I/O fencing:

Disk-based I/O fencing

I/O fencing that uses coordinator disks is referred to as disk-based I/O fencing.

Disk-based I/O fencing ensures data integrity in a single cluster.

Server-based I/O fencing

I/O fencing that uses at least one CP server system is referred to as server-based I/O fencing. Server-based fencing can include only CP servers, or a mix of CP servers and coordinator disks.

Server-based I/O fencing ensures data integrity in clusters.

In virtualized environments that do not support SCSI-3 PR, SFCFSHA supports non-SCSI-3 I/O fencing.

See About I/O fencing for SFCFSHA in virtual machines that do not support SCSI-3 PR.

Majority-based I/O fencing

Majority-based I/O fencing mode does not need coordination points to provide protection against data corruption and data consistency in a clustered environment.

Use majority-based I/O fencing when there are no additional servers and or shared SCSI-3 disks to be used as coordination points.

See About preventing data corruption with I/O fencing.


Symantec Corporation recommends that you use I/O fencing to protect your cluster against split-brain situations.

See the Storage Foundation Cluster File System High Availability Configuration and Upgrade Guide.