ALUA port group messages

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Environment

SUSE Linux Enterprise Server 12 Service Pack 2 (SLES 12 SP2)
SUSE Linux Enterprise Server 12 Service Pack 3 (SLES 12 SP3)

Situation

The following message are seen in the system log:

alua: port group 00 state A non-preferred supports tolUsNA
alua: port group 01 state N non-preferred supports tolUsNA

Resolution

The messages are informational only, they do not indicate any problem with the environment.

Cause

If the storage supports ALUA (Asymmetric Logical Unit Access), the messages show the detected port groups and their supported ALUA states.

Additional Information

Taking the following example:

alua: port group 00 state A non-preferred supports tolUsNA
alua: port group 01 state N non-preferred supports tolUsNA

Each letter in 'tolUsNA' represents an Asymmetrical Access State for a target port group being serviced by a LUN in a SCSI Multipath configuration:

Transitioning/Offline/LBA/Unavail/Standby/Non-Opt active/Active.

When a target port group is initialized and configured, that configuration dictates which of these possible Asymmetrical Access States the target port group can report with.

The states that are logged in capital letters are the Asymmetrical Access States which the currently reporting target port group is capable of undergoing for the given LUN.

To breakdown the logged information above:

'alua: port group 00'

This section of the message identifies which target port group is reporting, in this case, port group 00.

'state A preferred'

The current state of Asymmetrical Access that a target port group is in, out of the capable states it has reported to the output message. In this case, port group 00 is in the Active-Optimized state.

'supports tolUsNA'

The provided set of supported Asymmetrical Access States by the reporting target port group. In this case, Unavailable, Non-Optimized Active and Active-Optimized are supported states by the Multipath configuration for target port group 00.

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