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IBM SAN Volume Controller nodes are always installed in pairs, forming an I/O group. A minimum of one pair and a maximum of four pairs of nodes constitute a clustered SAN Volume Controller system. Many of the components that make up IBM SAN Volume Controller nodes include LEDs that indicate the status and activity of that component. 

Figure 13-1 shows the rear view, ports, and indicator lights on the IBM SAN Volume Controller node model 2145-SV1. 

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## Host interface cards 

The Fibre Channel (FC) or 10 Gbps Ethernet adapters are installed horizontally on the mid- and right sides of the node. The 2145-SV1 can accommodate up to four quad-port 16-Gbps FC cards, or one 4-port 10-gigabit Ethernet (GbE) adapter in a stand-alone configuration or in combination with an FC card. 

Table 13-1 lists the meaning of port LEDs for an FC configuration. 

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## USB ports 

Two active USB connectors are available in the horizontal position. They have no numbers and no indicators are associated with them. These ports can be used for initial cluster setup, encryption key backup, and node status or log collection. 

