Data ONTAP supports two storage connection types: Serial-Attached SCSI (SAS) and Fibre Channel (FC). The FC connection type supports three topologies: arbitrated loop, switched, and point-to-point.
SAS-connected storage shelves are connected to the controller on a daisy chain called a stack.
FC-connected storage shelves are connected to the controller on a loop.
You cannot combine different connection types in the same loop or stack.