Switched Mode Operation; Switched Mode Operation; Switched Mode Operation And Logical Equivalent - HP 316095-B21 - StorageWorks Edge Switch 2/24 Planning Manual

Planning Considerations for Fibre Channel Topologies
Although the architectural limit of a Fibre Channel arbitrated loop is 125 devices,
32 or fewer devices should be attached to the switch to avoid adversely impacting
loop performance. In particular, avoid attaching an excess number of servers or
high-bandwidth storage devices.

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
Part A of
pair of H_Ports, communicating at 1.0625 Gbps. Server S
D through a second switched pair of H_Ports, also communicating at 1.0625
2
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 S
Figure 29
S1
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.
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.
72
Figure 29 shows server S
shows the logical equivalent of this arbitrated loop.
Loop Switch
D1 S2
Figure 30 shows 8 hubs, each connected to a switch H_Port and each
connected to device D
1
and S or devices D
1 2
A
Logical Equivalent
H_Ports
S1
D2
SAN High Availability Planning Guide
Figure 29.
through a switched
1
is connected to device
2
and D . Part (B) of
1 2
B
D1 S2 D2