Coordinator disk requirements for I/O fencing

Last published : Sep 11, 2026
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.
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