About I/O fencing


About I/O fencing
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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:

The nodes that must retain access to the shared storage
The nodes that must be ejected from the cluster

This decision prevents possible data corruption. The installer installs the I/O fencing driver, VRTSvxfen RPM, when you install SF Oracle RAC. To protect data on shared disks, you must configure I/O fencing after you install and configure SF Oracle RAC.

I/O fencing technology uses coordination points for arbitration in the event of a network partition.

I/O fencing coordination points can be coordinator disks or coordination point servers (CP servers) or both. You can configure disk-based or server-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.

For detailed information, see the Symantec Cluster Server Administrator's Guide.

Review the following notes:

The CP server provides an alternative arbitration mechanism without having to depend on SCSI-3 compliant coordinator disks. Data disk fencing in CVM will still require SCSI-3 I/O fencing.
SF Oracle RAC requires at least 3 CP servers to function as coordination points in the cluster.

See the Symantec Storage Foundation for Oracle RAC Installation and Configuration Guide.

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