Specifications

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Compaq HSG80 Array Controller ACS Version 8.4 Configuration and CLI Reference Guide
As Figure 2–3 shows, only port 1 on controller A normally is active, which means it
presents LUNs 0–99 to the host. Similarly, port 2 on controller B normally is active,
which means it also presents LUNs, 100–199 to the host. If one controller fails, the
surviving controller automatically changes the standby port to an active port presents
the LUNs to the host.
Using Multiple-Bus Failover Mode
Multiple-bus (or host-assisted) failover is a dual-redundant controller configuration in
which each host port is active, having its own connection or path to the host. Thus, if
one of the host paths to a controller fails, the host can cause the units that became
inaccessible to failover to a remaining viable path. All units, 0–199, are presented
through all host ports, meaning that both controllers can present the same storage
units to the host if the other controller fails or loss of communication occurs.
To configure controllers for multiple-bus failover, follow the steps in “Configuring in
Multiple-Bus Failover Mode,” page 5–20.
Separate Port IDs
Figure 2–4 shows one example of a basic Fibre Channel Switched Fabric (FC-SW)
configuration in multiple-bus failover mode. In this example, all ports are active and
all ports have equal access to all LUNs, 0–199.
IMPORTANT: A unit is accessible by all four host ports. Because a unit is
assigned to one controller, the unit is considered
online and available to that
controller.