Chapter 8. MetroCluster 1098.4.1 Planning Fabric MetroCluster configurationsWhen planning and sizing Fabric MetroCluster environments, keep in mind theseconsiderations: Use FibreBridges in conjunction with SAS Shelves (EXN3000 & EXN3500). Provide enough ports/loops to satisfy performance (plan additional adapters ifappropriate). Storage must be symmetric (for example, same storage on both sides). For storage that isnot symmetric, but is similar, file a RPQ/SCORE. Keep in mind that N series native disk shelf disk drives are not supported withMetroClusters. Four Brocade/IBM B-Type Fibre Channel Switches are needed. For more informationabout supported Switches and firmware in Fabric MetroCluster environments, see theInteroperability Matrix at:http://www-304.ibm.com/support/docview.wss?uid=ssg1S7003897One pair of FC switches is required at each location. The switches need to be dedicatedfor the MetroCluster environment, and cannot be shared with other systems. Rememberthat you might need the following licenses for the Fibre Channel switches:– Extended distance license (if over 10km)– Full-fabric license– Ports-on-Demand (POD) licenses (for additional ports) Infrastructure / connectivity has these options:– Dark fiber: Direct connections by using long-wave Small Form-factor Pluggabletransceiver (SFPs) can be provided by customer. No standard offering is available forthese SFPs for large distances (> 30km).– Leased metro-wide transport services from a service provider: Typically provisioned bydense wavelength division multiplexer/time division multiplexer/optical add dropmultiplexer (DWDM/TDM/OADM) devices. Make sure that the device is supported byfabric switch vendor (IBM/Brocade).– Dedicated bandwidth between sites (mandatory): One inter-switch link (ISL) per fabric,or two ISLs if using the traffic isolation (TI) feature and appropriate zoning. Do not useISL trunking, because it is not supported, Take care in designing fabric MetroCluster infrastructure. Check ISL requirements andkeep in mind that cluster interconnect needs good planning and performance. Latency considerations: A dedicated fiber link has a round-trip time (RTT) ofapproximately 1 ms for every 100km (~ 60 miles). Additional nonsignificant latency mightbe introduced by devices (for example, multiplexers) en route. Generally speaking, asdistance between sites increases (assuming 100 km = 1 ms link latency):– Storage response time increases by the link latency. If storage has a response time of1.5 ms for local access, the response time increases by 1 ms to 2.5 ms over 100km.– Applications, in contrast, respond differently to the increase in storage response time.Some application response time increases by greater than the link latency. Forexample, application A response time with local storage access is 5 ms and over100km is 6 ms. Application B response time with local storage access is 5 ms, but over100km is 10ms. Take care in planning N6210 MetroCluster configurations, because the N6210 has onlytwo Fibre Channel initiator onboard ports and two PCI expansion slots. Because you useone slot for the FC/VI adapter, you have only one remaining slot for a Fibre Channel
