HP StorageWorks 2/24 FW 07.00.00/HAFM SW 08.06.00 McDATA Products in a SAN Env - Page 89
Shared Mode Versus Switched Mode, Logical Equivalent
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Planning Considerations for Fibre Channel Topologies 3 This section focuses on loop operation for Sphereon 4300 (12-port) and 4500 (24-port) Fabric Switches that operate at 1.0625 or 2.1250 gigabits per second (Gbps) and support FC-AL operation using FL_Ports and public and private device connectivity. Shared Mode Versus Switched Mode Legacy arbitrated loop switches (such as the McDATA ES-1000 Switch) are configured to operate in user-selectable shared or switched mode. NOTE: Sphereon 4300 and 4500 Fabric Switches do not support shared mode operation. Shared Mode Operation When set to shared mode, a switch acts as a hub implementing standard Fibre Channel arbitrated loop topology (although the loop has the physical appearance of a star configuration) and distributes the frame routing function through each loop port. When a loop circuit is initialized and established, arbitration protocol ensures only one device attached to a hub port (H_Port) owns the loop at a time. The port establishes communication with another device attached to an H_Port and allows the devices to transmit or receive frames. During frame transmission between these devices, the full bandwidth of the switch is used and no other H_Ports or devices are available for connection. When frame transmission completes, the loop circuit closes and other devices are able to contend for operation (using standard loop arbitration). Shared mode operation and its simplified logical equivalent are illustrated in Figure 3-1. A ES-1000 Switch H_Ports Logical Equivalent B D1 D2 S1 D1 D2 S1 Figure 3-1 Shared Mode Operation and Logical Equivalent Planning Considerations for Fibre Channel Topologies 3-3