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Another benefit of isolating remote application traffic on dedicated ports is to ensure that problems that affect the cluster-to-cluster interconnect do not adversely affect ports on the primary cluster. Adversely affected ports can deteriorate the performance of workloads that are running on the primary cluster. 

IBM suggests the port designations that are shown in Figure 9-5 for isolating port-to-local and port-to-remote node traffic for the 2145-SV1 nodes. (Other port configurations might apply for iSCSI and FCoE connectivity.) 

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Notes: Consider the following points regarding Figure 9-5: 

GLYPH<SM590000> SAN column assumes an odd/even SAN port configuration. Modifications must be made if other SAN connection schemes are used. 

GLYPH<SM590000> Use caution when zoning so that inter-node ports are not used for Host/Storage in the 8-, 12-, and 16-port configurations. 

GLYPH<SM590000> These options represent optimal configurations that are based on port assignment to function. The use of the same port assignment but different physical locations does not result in any significant performance effect in most client environments. 

This suggestion provides the traffic isolation that you want while also simplifying migration from existing configurations with only four ports, or even later migrating from 8-port, 12-port, or 16-port configurations to configurations with more ports. 

More complicated port mapping configurations that spread the port traffic across the adapters are supported and can be considered. However, these approaches do not appreciably increase the availability of the solution because the mean time between failures (MTBF) of the adapter is not significantly less than the MTBF of the non-redundant node components. 

Although alternative port mappings that spread traffic across HBAs might allow adapters to come back online following a failure, they do not prevent a node from going offline temporarily to restart and attempt to isolate the failed adapter and then, rejoin the cluster. Our suggestion takes all of these considerations into account with a view that the greater complexity might lead to migration challenges in the future and the simpler approach is best. 

