Multi-machine atomic seamless migration

A technique migrates data from source arrays to target arrays. The array devices operate in either active mode, passive mode, or stalled-active mode. The technique involves providing active-to-passive instructions to transition the source devices from active to passive while a host initially accesses host data from the source arrays using MPIO software (the target devices being in stalled-active mode), and monitoring whether the source devices successfully transition to passive during a predefined time period. If so, the technique involves operating the target devices in active mode and transferring data from the source devices to the target devices to enable the host to access the host data from the target arrays using the MPIO software. However, if a source device remains passive, the technique involves providing passive-to-active instructions to transition the source devices back to active to enable the host to access the host data from the source arrays.