Before You Configure Coordinator Disks

I/O fencing requires coordinator disks to be configured in a disk group that each cluster system can access. The use of coordinator disks enables the vxfen driver to resolve potential split-brain conditions and prevent data corruption. A coordinator disk is not used for data storage, so it can be configured as the smallest LUN on a disk array to avoid wasting space.

Coordinator disks must meet the following requirements:

  There must be at least three coordinator disks and the total number of coordinator disks must be an odd number. This ensures a majority of disks can be achieved.

  Each of the coordinator disks must use a physically separate disk or LUN.

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

  Coordinator disks in a disk array should use hardware-based mirroring.

  The coordinator disks must support SCSI-3 persistent reservations. Note that the use of the vxfentsthdw utility to test for SCSI-3 persistent reservation support requires that disks be 1MB or greater. Smaller disks can be tested manually. Contact VERITAS support (http://support.veritas.com) for the procedure.