58 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
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.
Additionally, a benefit is realized in isolating remote replication traffic to dedicated ports, and 
ensuring that any problems that affect the cluster-to-cluster interconnect do not affect all ports 
on the local cluster. 
IBM suggests the port designations for isolating both port-to-local and port-to-remote canister 
traffic for Storwize V7000 Gen2 and Gen2+ canisters, as shown in Figure 3-6.
Figure 3-6   Port masking configuration on Storwize V7000
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.