Technical data

connection is discovered. In transparent failover mode, host connections
to port 1 default to an offset of 0; host connections on port 2 default to an
offset of 100. Host connections on port 1 can see units 0 through 99; host
connections on port 2 can see units 100 through 199.
In multiple-bus failover mode, host connections on either port 1 or 2
can see units 0 through 199. In multiple-bus failover mode, the default
offset for both ports is 0.
If you change the failover mode from transparent failover to multiple-bus
failover, the offsets in the table of known connections remain the same as
if they were for transparent failover mode; the offset on port 2 remains
100. With an offset of 100 on port 2, a host cannot see units 0 through 99
on port 2. This reduces the availability. Also, if you have only a single
HSG80 controller and lose the connection to port 1, you lose access to
units 0 through 99.
Therefore, if you want to change from transparent failover to
multiple-bus failover mode, you must change the offset in the table of
known connections for each connection that has a nonzero offset.
_____________________ Note _____________________
Disconnecting and then reconnecting the cables does no good
because a connection that is added to the table remains in the
table until you delete the connection.
• The system can access a storage device through only one HSG80 port.
The system’s view of the storage device is not changed when the HSG80
is placed in multiple-bus failover mode.
In transparent failover mode, the system accesses storage units D0
through D99 through port 1 and units D100 through D199 through port
2. In multiple-bus failover mode, you want the system to be able to
access all units through all four ports.
6.10.2 Procedure to Convert from Transparent to Multiple-bus
Failover Mode
To change from transparent failover to multiple-bus failover mode by
resetting the unit offsets and modifying the systems’ view of the storage
units, follow these steps:
1. Shut down the operating systems on all host systems that are accessing
the HSG80 controllers that you want to change from transparent
failover to multiple-bus failover mode.
Using Fibre Channel Storage 6–77