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Setting up coordinator disk groups

I/O fencing requires coordinator disks that are configured in a disk group and accessible to each node in the cluster. These disks enables the vxfen driver to resolve potential split brain conditions and prevent data corruption. Make sure to meet the requirements for coordinator disks and then create the coordinator disk group.

Requirements for coordinator disks

After adding and initializing disks for use as coordinator disks, make sure coordinator disks meet the following requirements:

• You must have three coordinator disks.
• Each of the coordinator disks must use a physically separate disk or LUN.
• Each of the coordinator disks should exist on a different disk array, if possible.
• You must initialize each disk as a VxVM disk.
• The coordinator disks must support SCSI-3 persistent reservations.

  See Testing the shared disks for SCSI-3

• The coordinator disks must exist in a disk group (for example, vxfencoorddg).

  See Creating the coordinator disk group and setting the coordinator attribute

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

Creating the coordinator disk group and setting the coordinator attribute

From one node, create a disk group named vxfencoorddg. This group must contain three disks or LUNs.

You must also set the coordinator attribute for the coordinator disk group. VxVM uses this attribute to prevent the reassignment of coordinator disks to other disk groups.

Note that if you create a coordinator disk group as a regular disk group, you can turn on the coordinator attribute in Volume Manager. You do this with a vxdg set coordinator=on command.

Refer to the Veritas Volume Manager Administrator's Guide for details on creating disk groups.

The example procedure assumes that the disks have the device names c1t1d0, c2t1d0, and c3t1d0.

 To create the vxfencoorddg disk group

• On any node, create the disk group by specifying the device name of the disks:

  # vxdg -o coordinator=on init vxfencoorddg c1t1d0 c2t1d0 c3t1d0