If ALUA only applies to FCP, then what do the commands "iscsi tpgroup alua set <tpgroup_name> { optimized | nonoptimized } [preferred]" and "iscsi tpgroup show" do?
Asymmetric Logical Unit Access (ALUA) management Data ONTAP supports SCSI ALUA functionality for managing multi-pathed SCSI devices. ALUA provides a standardized mechanism for path discovery and prioritization. Devices are identified by target port IDs, which are then grouped into target port groups Each group has a state which, when configured, enables the host multipathing software to select the appropriate path priorities when accessing a LUN.
For iSCSI, ALUA settings are controlled at the target portal group level using the iscsi tpgroup alua set command. A target portal group can be configured to be either optimized or non-optimized; a host typically uses all the optimized paths before using any non-optimized paths it may find. All target portal groups are optimized by default.
There is also an optional preferred setting that may be used on a target portal group. Check your host's multipathing software documentation to see if it supports ALUA and the preferred setting.
ALUA is enabled on Initiator Groups using the igroup set command. All LUNs mapped to an ALUA enabled igroup will support ALUA functionality.
iscsi tpgroup alua show
Display the ALUA settings for all iSCSI target portal groups.
iscsi tpgroup alua set <tpgroup_name> { optimized | nonoptimized } [preferred]
Configure ALUA priorities for a target portal group. If the preferred argument is not given then the target portal group will not be configured as preferred.