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Redundant Controller
10-9
How does Failover and Failback Work?
A. Channel Bus
Below is a sample illustration of the redundant controller operation:
Figure 10 - 7 Redundant Controller Channel Bus
The host computer is connected to both the Primary and the
Secondary controllers. Each controller has two of its SCSI/Fibre
channels assigned as the host channels, and the other SCSI/Fibre
channels assigned to drive connections.
There are two logical drives. Logical drive 0 is assigned to the
Primary controller (mapped to the Primary ID), and logical drive 1
assigned to the Secondary controller (mapped to the Secondary ID).
Should one controller fail, the existing controller will manage the
logical drive once belonged to the failed controller via the once
inactive ID (the standby ID).
The ID mapping is synchronized between the controllers. In fact, all
the configuration settings can be done only through the Primary
controller. See the table below: