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. However, for MetroCluster configurations, the FC and SAS connection types can be combined in a bridged connection, with FC on the controller side and SAS on the shelf side. The bridged connection can be used in either a direct-attached or switched topology. For more information, see Configuring a MetroCluster system with SAS disk shelves and FibreBridge 6500N bridges.