Справочник Пользователя для IBM Flex System V7000 Expansion Enclosure 4939H29

Draft Document for Review January 29, 2013 12:52 pm

IBM Flex System V7000 Storage Node Introduction and Implementation Guide

Fibre Channel provides three distinct and one hybrid interconnection topologies. By having 
more than one interconnection option available, a particular application can choose the 
topology that is best suited to its requirements.

The three Fibre Channel topologies are:

– Point-to-point, the point-to-point topology consists of a single connection between two 

nodes. All the bandwidth is dedicated to these two nodes. 

– Arbitrated loop, Loop, in the loop topology, the bandwidth is shared between all the 

nodes connected to the loop. The loop can be wired node-to-node; however, if a node 
fails or is not powered on, the loop is out of operation. This is overcome by using a hub. 
A hub opens the loop when a new node is connected, and closes it when a node 
disconnects. Although more popular a number of years ago when FC speeds were 
slower, this topology is rarely used now. 

– Switched or fabric, a switch allows multiple concurrent connections between nodes. 

There can be two types of switches: circuit switches and frame switches. Circuit 
switches establish a dedicated connection between two nodes, where as frame 
switches route frames between nodes and establish the connection only when needed. 
This is also known as switched fabric.

The point-to-point topology is used within the IBM Flex System Enterprise Chassis switch 
between the compute node and the I/O Module FC switch. Also between the switch and IBM 
Flex System V7000 Storage Node. The switch or fabric topology is used between the IBM 
Flex System Enterprise Chassis switches and external FC SAN.

Figure 11-19 on page 459 shows the point to point topology used in the FC connectivity within 
the IBM Flex System Enterprise Chassis. In this example there is a switched topology 
between the I/O Module switch FC3171 and the external FC switch.