Traffic Distribution And Failover Process - Compaq External RAID Controller & Subsystem Infortrend Operation Manual

Redundant Controller
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
Host LUN Mapping
Logical Drive Assignment
Drive Channel
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:
Host Chl SCSI ID
Drive Chl SCSI ID
Logical Drive 0
ID0 / LUN * (PID)
Primary
2
Primary Controller ID
PID = 0
7 (or 8 for the dual
redundant chassis)
Logical Drive 1
ID1 / LUN * (SID)
Secondary
3
Secondary Controller ID
SID = 1
6 suggested (or 9 for the
dual redundant chassis)
10-12