What ALUA is

Data ONTAP 7.2 added support for the Asymmetric Logical Unit Access (ALUA) features of SCSI, also known as SCSI Target Port Groups or Target Port Group Support.

ALUA is an industry standard protocol for identifying optimized paths between a storage system and a host. ALUA enables the initiator to query the target about path attributes, such as primary path and secondary path. It also allows the target to communicate events back to the initiator. It is beneficial because multipathing software can be developed to support any array; proprietary SCSI commands are no longer required.

Note: You cannot enable ALUA on iSCSI igroups.

Attention: You must ensure that your host supports ALUA before enabling it. Enabling ALUA for a host that does not support it can cause host failures during cluster failover.