Specifications

Chapter 6 Troubleshooting Common Problems 6-3
The symptoms of obtrusive array controllers may be the successful completion of
some commands, particularly non data access commands. Many data access
commands may fail on one or both controller in the subsystem. Other symptoms
include frequent command time-outs amidst many successful command
operations.
■ Failed Inter-controller Communication (ICON) Path
Redundant controllers rely on the ICON channel, which may be a dedicated
Application-specific Integrated Circuit (ASIC). The failed inter-controller
communication path condition occurs when the communication path between the
two array controllers has failed due to a communication line failure on one of the
controllers. The controllers have the communications capability to function in the
active/passive mode without the use of the ICON channel.
Diagnostics are run on the ICON channel at power up. Therefore, ICON channel
failures maybe detected at Start Of Day (SOD). If you are going through the serial
port and such a failure was detected, the controller’s Diagnostic Manager will
provide the option to the user to abort the power up sequence and replace the
controller.
The failure of the ICON channel may cause some of the following situations to
arise:
■ Switching from any mode of operation to dual/active mode is not allowed.
■ Logical unit ownership transfers are not allowed.
■ Changes in drive status for example from Optimal to Failed.
■ Changes in LUN status for example from Degraded to Optimal.
■ The addition of a logical unit to one controller will not be seen by the other
controller until the next reset or power up causes both controllers to read the
array configuration stored on the disk drives.
■ The deletion of a logical unit owned by one controller will not be seen by the
alternate controller until the next reset or power up.
6.1.2 Failing a Controller in Dual/Active Mode
If the host determines that a controller operating in dual/active mode has failed, it
may hold this controller in reset. To prevent loss of access to the LUNs owned by
this controller, the host must switch mode of operation to active/failed (passive)
mode.
The host should issue a mode select to the redundant controller page to the non-
failed controller. This requires setting the alternate RDAC mode parameters to failed
alternate controller (0x0C).