HP Surestore 64 FW 05.01.00 and SW 07.01.00 HP StorageWorks SAN High Availabil - Page 70
Switched Mode Operation, Switched mode operation and logical equivalent,
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Planning Considerations for Fibre Channel Topologies Switched Mode Operation When set to switched mode (default setting), a loop switch enables frame transmission through multiple point-to-point connected pairs. Switched mode operation and its simplified logical equivalent are illustrated in Figure 29. Part (A) of Figure 29 shows server S1 connected to device D1 through a switched pair of H_Ports, communicating at 1.0625 Gbps. Server S2 is connected to device D2 through a second switched pair of H_Ports, also communicating at 1.0625 Gbps. Because of opportunistic bandwidth sharing, the two switched pairs effectively increase the switch bandwidth to 2.125 Gbps. The remaining switch H_Ports (four ports) are available for switched connection to each other, but cannot communicate with servers S1 and S2 or devices D1 and D2. Part (B) of Figure 29 shows the logical equivalent of this arbitrated loop. A Logical Equivalent B Loop Switch H_Ports S1 D1 S2 D2 S1 D1 S2 D2 Figure 29: Switched mode operation and logical equivalent Switched mode also allows independent operation of looplets of devices, each connected through an unmanaged hub, and each attached to a single switch H_Port. Figure 30 shows 8 hubs, each connected to a switch H_Port, and each connected to a pair of devices (16 devices total). Each device pair forms a looplet that communicates through a hub and connecting H_Port, and because of opportunistic bandwidth sharing, the looplets effectively increase the switch bandwidth to 8.5 Gbps. 70 SAN High Availability Planning Guide