CPU/IO module status
The CPU/IO module (0 or 1) that is started first is managed as the primary, and the module started later is managed as the secondary. If one CPU/IO module is disconnected because of a failure, the other module becomes the primary.
The CPU/IO module to be started first is selected depending on the primary/secondary status of modules when the server was shut down the last time.
The following devices are connected to the primary CPU/IO module by the connectors on the system backplane and access both CPU/IO modules 0 and 1. When one CPU/IO module is disconnected because of a failure, those are switched to the other module automatically and continue operating.
Note: Both CPU/IO modules 0 and 1 can access the optical disk drive. If one
CPU/IO module is isolated because of a failure, only the active (Primary)
CPU/IO module can access the drive.
Note: The drive letter of the optical disk drive is reallocated
automatically. The unused letter is allocated to the drive in the order of D to
Z. If you want to set the fixed drive letter to the optical disk drive, specify
the letter which is not allocated in the order of D to Z after setting the hard
disk drive letter.