Fujitsu MBA3073FD, Product Manual

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General Description
1.3 System Configuration
For the Fibre Channel, the ANSI standard defines Arbitrated Loop, Fabric, and Point-to-Point
technologies. The HDDs support the Arbitrated Loop technology. Figure 1.1 gives an example of
the FC-AL system configuration.
HDD
(Node-3)
HDD
(Node-2)
Port A
Port B
Port A
Port B
Port A
Port B
BC
BC
BC
BC
BC
BC
Port A BC
HDD
(Node-4)
Initiator
(Node-1)
Port B
BC
Figure 1.1 Example of FC-AL system configuration
Any device connected to the Fibre Channel is called a loop. The nodes shown in Figure 1.1 represent
the initiator and individual HDDs. Each node has at least one port called an N_port. For FC-AL,
each port is called a Node-Loop port (NL_port).
The HDDs have two ports, one of which is used for connections to an FC-AL. A maximum of 126
NL_ports can be connected to a single port.
(1) Loop
configuration
A port embedded with sending and receiving circuits uses differential signals to send and receive data
on electric signal lines. A pair of signal lines is called a link. Since signals are sent in one direction
on a link, the links in a system must be connected to form a loop. The FC-AL interface sends and
receives data via nodes on the loop. Therefore, if a node connected to a loop is powered off or the
interface signals of a node cannot be sent or received correctly, the loop does not work normally. A
common solution preventing this problem from occurring is to add a port bypass circuit on the back
plane of the system. BC in Figure 1.1 indicates the port bypass circuit.
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