Table 10 - 1 Id Mapping Status (Normal Operation); Table 10 - 2 Id Mapping Status (Controller Failed) - Compaq External RAID Controller & Subsystem Infortrend Operation Manual

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Table 10 - 1 ID Mapping Status (Normal Operation)

Channel
0 0 (Primary ID)
1 (Secondary ID)
1 1 (Secondary ID)
0 (Primary ID)
In the event of controller failure (say, the Primary controller fails), the
once inactive ID (chip) will become active:

Table 10 - 2 ID Mapping Status (Controller Failed)

Channel
0 0 (Primary ID)
1 (Secondary ID)
1 1 (Secondary ID)
0 (Primary ID)
Figure 10 - 8 Controller Failover
For every channel that is actively serving I/Os, there is another on the
alternate controller that stays idle and will inherit the task should its
counterpart fail.
An exception to this is that active IDs may co-exist on single or
multiple host channels.
concern, then standby chips may not be necessary.
ID Status
Active
Standby
Active
Standby
ID Status
Active
Standby- becomes
Active!
Active
Standby
As long as I/O bandwidth is not of the
Target Chip
Pri. Controller
channel 0
Sec. Controller
channel 0
Sec. Controller
channel 1
Pri. Controller
channel 1
Target Chip
Pri. Controller
channel 0 – Failed!
Sec. Controller
channel 0
Sec. Controller
channel 1
Pri. Controller
channel 1- Failed!
Infortrend