The coordination points can either be disks or servers or both. Typically, a cluster must have three coordination points.

• 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 Storage Foundation configuration.

  You can configure coordinator disks to use Veritas Volume Manager Dynamic Multipathing (DMP) feature. Dynamic Multipathing (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 either DMP devices or the underlying raw character devices. I/O fencing uses SCSI-3 disk policy that is either raw or dmp based on the disk device that you use. The disk policy is dmp by default.

  See the Veritas Volume Manager 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 SF HA cluster nodes to perform the following tasks:

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

  • Check which other nodes are registered as members of this activeSF HA cluster

  • Self-unregister from this activeSF HA cluster

  • Forcefully unregister other nodes (preempt) as members of this active SF HA 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 SF HA cluster.

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