Dell EMC Metro node 7.0.1 Administrator Guide

Active-passive array

An active-passive array typically has two controllers and provides active-passive access to a Logical Unit (LU) through a set of target ports. The access types of these ports are Active (ACT) or Passive (PAS). Active is used for I/O and passive cannot be used for I/O. When active paths to logical units are lost, the initiator (metro node) can decide to activate passive paths to perform I/Os by sending vendor specific SCSI commands to the array.

The controller with the active target ports for a specific logical unit is referred to as Active (ACT) controller of that logical unit. The controller with passive target ports for a specific logical unit is referred to as Passive (PAS) controller of that logical unit. The controller which is active for a logical unit can be a passive controller for some other logical unit and vice versa.