Make sure that the I/O fencing coordinator disks meet the following requirements:
For disk-based I/O fencing, you must have at least three coordinator disks or there must be odd number of coordinator disks.
The coordinator disks must be DMP devices.
Each of the coordinator disks must use a physically separate disk or LUN.
Veritas 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.
Coordinator devices can be attached over iSCSI protocol but they must be DMP devices and must support SCSI-3 persistent reservations.
Veritas 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 coordinator disk size must be at least 128 MB.