GLYPH<SM590000> The RC buffer size setting must be 512 MB on each system in the partnership. This setting  can be accomplished by running the  chsystem -rcbuffersize 512  command on each  system. GLYPH<SM590000> Two Fibre Channel ports on each node that will be used for replication must be dedicated  for replication traffic. This configuration can be achieved by using SAN zoning and port  masking. GLYPH<SM590000> SAN zoning should be applied to provide separate intrasystem zones for each  local-remote I/O group pair that is used for replication. See “Remote system ports and  zoning considerations” on page 187 for further zoning guidelines. GLYPH<SM590000> Mirrored foreground writes, as generated by your server applications at peak times GLYPH<SM590000> Background resynchronization, for example, after a link outage GLYPH<SM590000> Inter-system heartbeat Important:  Changing this setting is disruptive to Metro Mirror and Global Mirror  operations. Use this command only before partnerships are created between systems,  or when all partnerships with the system are stopped. IBM Spectrum Virtualize uses part of the bandwidth for its internal intersystem heartbeat. The  amount of traffic depends on how many nodes are in each of the local and remote systems.  Table 6-7 shows the amount of traffic (in megabits per second) that is generated by different  sizes of systems. These numbers represent the total traffic between the two systems when  no  I/O is occurring  to a mirrored volume on the remote system. Half of the data is sent by one system, and half of  the data is sent by the other system. The traffic is divided evenly over all available  connections. Therefore, if you have two redundant links, half of this traffic is sent over each  link during fault-free operation. If the link between the sites is configured with redundancy to tolerate single failures, size the  link so that the bandwidth and latency statements continue to be accurate even during single  failure conditions. Proper network sizing is essential for the remote copy services operations. Failing to estimate  the network sizing requirements can lead to poor performance in remote copy services and  the production workload. Consider that intersystem bandwidth should be capable of supporting the combined traffic of  the following items: Network sizing considerations Link bandwidth that is used by internode communication Table 6-7 IBM Spectrum Virtualize intersystem heartbeat traffic (megabits per second) Local or remote system Two nodes Four nodes Six nodes Eight nodes Two n odes 5 6 6 6 Four nodes 6 10 11 12 Six nodes 6 11 16 17 Eight nodes 6 12 17 21 Chapter 6. Copy services  181