About planning to configure I/O fencing
After you configure VCS with the installer, you must configure I/O fencing in the cluster for data integrity. Application clusters on release version 7.4 (HTTPS-based communication) only support CP servers on release version 6.1 and later.
You can configure disk-based I/O fencing, server-based I/O fencing, or majority-based I/O fencing. If your enterprise setup has multiple clusters that use VCS for clustering, Veritas recommends you to configure server-based I/O fencing.
The coordination points in server-based fencing can include only CP servers or a mix of CP servers and coordinator disks.
Veritas also supports server-based fencing with a single coordination point which is a single highly available CP server that is hosted on an SFHA cluster.
Warning: For server-based fencing configurations that use a single coordination point (CP server), the coordination point becomes a single point of failure. In such configurations, the arbitration facility is not available during a failover of the CP server in the SFHA cluster. So, if a network partition occurs on any application cluster during the CP server failover, the application cluster is brought down. Veritas recommends the use of single CP server-based fencing only in test environments.
You use majority fencing mechanism if you do not want to use coordination points to protect your cluster. Veritas recommends that you configure I/O fencing in majority mode if you have a smaller cluster environment and you do not want to invest additional disks or servers for the purposes of configuring fencing.
Note: Majority-based I/O fencing is not as robust as server-based or disk-based I/O fencing in terms of high availability. With majority-based fencing mode, in rare cases, the cluster might become unavailable.
If you have installed VCS in a virtual environment that is not SCSI-3 PR compliant, you can configure non-SCSI-3 fencing.
Figure: Workflow to configure I/O fencing illustrates a high-level flowchart to configure I/O fencing for the VCS cluster.
Figure: Workflow to configure I/O fencing
Figure: Workflow to configure non-SCSI-3 I/O fencing illustrates a high-level flowchart to configure non-SCSI-3 I/O fencing for the VCS cluster in virtual environments that do not support SCSI-3 PR.
Figure: Workflow to configure non-SCSI-3 I/O fencing
After you perform the preparatory tasks, you can use any of the following methods to configure I/O fencing:
You can also migrate from one I/O fencing configuration to another.
See the Storage foundation High Availability Administrator's Guide for more details.