Symantec 5 manual I/O fencing configuration files include

Configuring VCS clusters for data integrity	91
About setting up disk-based I/O fencing

For the latest information on supported hardware visit the following URL: http://entsupport.symantec.com/docs/283161

■Each of the coordinator disks must use a physically separate disk or LUN. Symantec recommends using the smallest possible LUNs for coordinator disks.

■Each of the coordinator disks should exist on a different disk array, if possible.

■The coordinator disks must support SCSI-3 persistent reservations.

■Symantec recommends using hardware-based mirroring for coordinator disks.

■Coordinator disks must not be used to store data or must not be included in disk groups that store user data.

■Coordinator disks cannot be the special devices that array vendors use. For example, you cannot use EMC gatekeeper devices as coordinator disks.

The I/O fencing configuration files include:

/etc/vxfendg	You must create this file to include the coordinator disk
	group information.
/etc/vxfenmode	You must set the I/O fencing mode to SCSI-3.
	You can configure the vxfen module to use either DMP
	devices or the underlying raw character devices. Note that
	you must use the same SCSI-3 disk policy on all the nodes.
	The SCSI-3 disk policy can either be raw or dmp. The policy
	is raw by default. If you use iSCSI devices, you must set the
	disk policy as dmp.