Storage redundancy and multipathing
Redundancy is one of the keywords of IT, where any single component failure could mean big problems for a company or its customers. The general design principle of avoiding SPOF is something that we should always stick to. At the end of the day, no network adapter, cable, switch, router, or storage controller is going to work forever. So, calculating redundancy into our designs helps our IT environment during its normal life cycle.
At the same time, redundancy can be combined with multipathing to also ensure higher throughput. For example, when we connect our physical host to FC storage with two controllers with four FC ports each, we can use four paths (if the storage is active-passive) or eight paths (if it's active-active) to the same LUN(s) exported from this storage device to a host. This gives us multiple additional options for LUN access, on top of the fact that it gives us more availability, even in the case of failure.