Enabling the S2D feature inside the Windows Failover Cluster settings automatically enables Storage Bus Layer (SBL) as well.SBL provides a virtual Initiator and Target to each node. SBL uses block over SMB3 and SMB Direct as the transport for communication between the servers in the cluster. SBL allows each node to see all disks of all the nodes within the same cluster. The disks are then aggregated within a shared Storage Pool.