In a fully redundant dual fabric environment, the core switch in one of the fabrics fails. None of the servers can access their LUNs. Which of the following is a possible cause of this issue?

If the storage controllers were only connected to a single fabric, then the failure of that fabric's core switch would sever all paths from the storage array to the servers. Despite having a second, functional fabric, the storage itself would be isolated, making all LUNs inaccessible.

Port zoning is a valid and common security mechanism in a Fibre Channel fabric and its presence alone does not cause a complete loss of LUN access in a dual-fabric setup during a single fabric failure.

Insufficient buffer-to-buffer credits typically lead to performance issues and congestion, not a complete and simultaneous loss of LUN access for all servers when one fabric fails.

While LUNs being zoned to only one fabric would cause access loss if that fabric fails, the problem statement implies a more systemic issue affecting all LUNs and servers, pointing to the underlying storage connectivity rather than just zoning configurations within a fabric.