||Oracle Tips by Burleson
Disk I/O Tuning
Channel Arbitrated Loops (FC-AL) use a loop structure to attach
multiple nodes without the use of hubs and switches. Arbitration is
used by the node ports to establish a point-to-point circuit. FC-AL
is a distributed topology where each L_Port includes the minimum
necessary function to establish the circuit. From two to 126 node
ports can be connected using the arbitrated loop topology. Figure
2-5 shows a four-node arbitrated loop setup.
Four-Node Arbitrated Loop Set Up
arbitrated loop topology the ports are called NL_Ports (Node Loop
Ports). Each of the NL_Ports has an input and output connection. The
actual ports are located on the host’s backpanel, not on the disk
drive. Dual ports are usually provided for redundancy so that if one
loop fails, the other one can fulfill the loop duties. Each disk
drive usually has one Fibre Channel single connector attachment (SCA)
arbitrated loop protocol is known as a token acquisition protocol.
This means each port on the same arbitrated loop sees all messages,
but only takes messages that are addressed to it, passing along all
The above text is
an excerpt from:
Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle
by Mike Ault
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