Compaq Infortrend manual How does Failover and Failback Work? A. Channel Bus

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:

Redundant Controller 10-9