I am not sure how many people remember Cisco SANTap. About ten years ago, Cisco introduced a data tapping mechanism in the MDS 9000 fibre channel switches. The idea was to allow the data path to be “tapped” at-will. Tapping in this case meant using a mechanism in the switch to split the data being written from client hosts to the storage, allowing the identical “split” data to be routed through a second, separate path.
SANTap therefore allowed a copy of the data to be seamlessly “mirrored” through the switch and subsequently used by other applications for multiple purposes (especially for backup). It facilitated real-time protection of critical data, and allowed advanced functions such as migration, snapshots, etc.