The coordination points can either be disks or servers or both.

• Coordinator disks

  Disks that act as coordination points are called coordinator disks. Coordinator disks are three standard disks or LUNs set aside for I/O fencing during cluster reconfiguration. Coordinator disks do not serve any other storage purpose in the VCS configuration.

  You can configure coordinator disks to use Veritas Volume Manager's Dynamic Multi-pathing (DMP) feature. Dynamic Multi-pathing (DMP) allows coordinator disks to take advantage of the path failover and the dynamic adding and removal capabilities of DMP. So, you can configure I/O fencing to use DMP devices. I/O fencing uses SCSI-3 disk policy that is dmp-based on the disk device that you use.

  Note:

  The dmp disk policy for I/O fencing supports both single and multiple hardware paths from a node to the coordinator disks. If few coordinator disks have multiple hardware paths and few have a single hardware path, then we support only the dmp disk policy. For new installations, Symantec only supports dmp disk policy for IO fencing even for a single hardware path.

  See the Storage Foundation Administrator's Guide.

• Coordination point servers

  The coordination point server (CP server) is a software solution which runs on a remote system or cluster. CP server provides arbitration functionality by allowing the SFHA cluster nodes to perform the following tasks:

  • Self-register to become a member of an active VCS cluster (registered with CP server) with access to the data drives

  • Check which other nodes are registered as members of this active VCS cluster

  • Self-unregister from this active VCS cluster

  • Forcefully unregister other nodes (preempt) as members of this active VCS cluster

  In short, the CP server functions as another arbitration mechanism that integrates within the existing I/O fencing module.

  Note:

  With the CP server, the fencing arbitration logic still remains on the VCS cluster.

  Multiple VCS clusters running different operating systems can simultaneously access the CP server. TCP/IP based communication is used between the CP server and the VCS clusters.