Shared Mode Operation; Shared Mode Operation And Logical Equivalent - HP StorageWorks 64 - SAN Director Switch Planning Manual

Shared Mode Operation

When set to shared mode, a loop switch implements standard Fibre Channel
arbitrated loop topology, and distributes the frame routing function through each
loop port. Shared mode operation and its simplified logical equivalent are
illustrated in
D1
Figure 27: Shared Mode operation and logical equivalent
Part (A) of
H_Ports, and communicating at 1.0625 Gbps. Although the remaining switch
H_Ports (six ports) and device D
between device D
H_Ports, device D
communication pair and the NL_Port on device D
that allows frames to pass around the loop at the full switch bandwidth.
Part (B) of
frame transmission between device D
closes and other ports attached to initiating devices arbitrate for loop access.
When operating in shared mode, the switch is a serially reusable resource that
provides service access to all ports on the loop. Access is granted by successful
arbitration. When arbitration is won by a device, the loop is busy and other
arbitrating devices must wait for loop access.
Device attachment and loop construction are not limited to the eight switch
H_Ports. Through the use of cascaded unmanaged hubs, the Fibre Channel
architectural limit of 125 FC-AL devices can attach to the switch. For example,
Figure 28
two unmanaged hubs.
SAN High Availability Planning Guide
Figure 27.
Loop Switch
D2
Figure 27 shows device D
and server S
1
, device D , and server S
1 2
Figure 27 shows the logical equivalent of this arbitrated loop. When
shows a private loop composed of a loop switch, 20 FC-AL devices, and
Planning Considerations for Fibre Channel Topologies
A
H_Ports
S1
connected to server S
1
are unavailable for connection, frame traffic
2
travels through a loop that consists of all eight
1
Each H_Port not participating in the
1.
provide a repeater function
2
and server S
1 1
Logical Equivalent
D1 D2
S1
through a pair of
1
completes, the loop circuit
B
67