Compaq Infortrend manual D. Traffic Distribution and Failover Process, 9 Traffic Distribution

D. Traffic Distribution and Failover Process

The diagram below illustrates a four-channel configuration using channel 0 as the communications path. Channel 1 serves as the host interface and multiple IDs are created to facilitate active-active operation. Each controller occupies either a Primary ID or a Secondary ID on drive channels. One logical unit is assigned to the Primary controller and the other the Secondary controller. In the event when one controller fails, the existing controller will inherit IDs from the failed controller and continue I/Os.

Figure 10 - 9 Traffic Distribution

	Logical Drive 0	Logical Drive 1
Host LUN Mapping	ID0 / LUN* (PID)	ID1 / LUN* (SID)
Logical Drive Assignment	Primary	Secondary
Drive Channel	2	3

When creating a logical unit, users will be prompted to assign the logical unit either to the Primary or to the Secondary controller. Once the assignment is done, logical unit(s) assigned to the Primary controller can only be mapped to the Primary IDs on host channel; Logical unit(s) assigned to the Secondary controller can only be mapped to the Secondary IDs on host channel.

The channel ID (Primary/Secondary) assignment for a SCSI controller should look like this:

	Primary Controller ID	Secondary Controller ID
Host Chl SCSI ID	PID = 0	SID = 1
Drive Chl SCSI ID	7 (or 8 for the dual	6 suggested (or 9 for the
	redundant chassis)	dual redundant chassis)

Redundant Controller 10-12