Automatic Switching of Metadisks

Metadisks can be automatically switched from the active path to the alternate path in two situations:

• The active path fails.

• The board containing the controller for the active path is detached by using a DR Detach operation. (Automatic switching during a DR detach is available only on the Sun Enterprise 10000 server.)

When the active path fails, an automatic switch is attempted only if an alternate path is available. The failed path is then marked unavailable, or tried. You can identify the tried paths with apconfig -S:

# apconfig -S

c1      pln0  P A
c2      pln1  T
        metadiskname(s):
                mc1t5d0  
                mc1t4d0   
                mc1t3d0   
                mc1t2d0   
                mc1t1d0   
                mc1t0d0   

In this example, the currently inactive path, pln1, is marked with a "T", which indicates that path was tried but failed.

The tried flag is only significant for automatic switch operations (not for manual switch operations). AP never attempts to automatically switch to a tried path. (This prevents thrashing in the case that both paths may have failed.)

You can reset the tried flag with any of the following actions:

• Reboot the corresponding domain.

• Perform a DR detach followed by a DR attach of a board that contains the controller marked as tried.

• Manual reset the tried flag for a particular controller.

You can manually reset the tried flag as shown in this example:

# apdisk -w pln1

In this example, pln1 is a controller with the tried flag set to true. The apdisk -w feature should be used judiciously. This command merely clears the tried flag; it does not address any potential problems with the controller or device. This command should only be used in situations where the failed path has been restored without an intervening DR operation or reboot.

Note that you can attempt to perform a manual switch to a path that is marked as tried.