text: **Important:**If you zone two Fibre Channel ports on each node in the local system to two 
  Fibre Channel ports on each node in the remote system, you can limit the effect of severe 
  and abrupt overload of the intercluster link on system operations. 
  
  If you zone all node ports for intercluster communication and the intercluster link becomes 
  severely and abruptly overloaded, the local FC fabric can become congested so that no FC 
  ports on the local Storwize V7000 nodes can perform local intracluster heartbeat 
  communication. This situation can, in turn, result in the nodes experiencing lease expiry 
  events. 
  
  In a lease expiry event, a node restarts to attempt to reestablish communication with the 
  other nodes in the clustered system. If the leases for all nodes expire simultaneously, a 
  loss of host access to volumes can occur during the restart events. 
  
  For more information about zoning best practices, see IBM System Storage SAN Volume 
  Controller and Storwize V7000 Best Practices and Performance Guidelines, SG24-7521. 
  
  **3.6.7 Port designation recommendations**
  
  The intracluster communication is used for mirroring write cache and metadata exchange 
  between nodes, and is critical to the stable operation of the cluster. It is possible to upgrade 
  nodes beyond the standard 4 FC port configuration. Such upgrade provides an opportunity to 
  dedicate ports to local node traffic, separating them from other cluster traffic on the remaining 
  ports. This configuration provides a level of protection against malfunctioning devices and 
  workload spikes that might otherwise impact the intracluster traffic. 