SECURING FIBRE CHANNEL FABRICS - Brocade

Chapter 3: SAN Basics for Security ProfessionalsServer withMPIO softwareFabric BFabric ADisk arrayFigure 8. Dual-fabric designDual-fabric design is a best practice and should always be used withdisk environments. A dual-fabric architecture provides redundantpaths to avoid any single points of failure. This is very different from atypical LAN architecture but the impact of a failed access to a diskdrive cannot be tolerated as it takes more time to recover from suchan event. Converged networks, IP/FC, are particularly problematic asthe architecture of each type of network is very different. Tape environments,however, would not benefit from a dual-fabric architecture,since tape drives and backup applications do not have the capability ofbeing dual attached.Cascade TopologyA cascaded fabric is the simplest architecture; switches are daisychainedtogether to form a string of switches. Middle switches are connectedto two other switches and the two end switches are connectedonly to one other switch. Figure 16 illustrates a four-switch (on the left)and a six-switch (on the right) cascade topology. A disadvantage of thistopology is that a server attached to Switch A in the six-switch topologywould have to traverse four other switches to get to its storage if the storagedevice were attached to switch F. These multiple hops can degradeperformance. For example, if all of the storage devices were attached toswitch F and every port on switches A to E were connected to a host, thetraffic between switches E and F could become highly congested.36 Securing Fibre Channel Fabrics