A systems administrator is troubleshooting a physical server that hosts multiple virtual machines. The administrator finds that all virtual machines are offline and all datastores connected via a Fibre Channel (FC) SAN are inaccessible from this host only. Other servers connected to the same SAN are functioning correctly. The host's system logs are filled with I/O timeout errors and pathing failures to all LUNs. Which of the following is the MOST likely cause of this issue?
The correct answer is a failed Host Bus Adapter (HBA). An HBA is a hardware card that connects a server to a storage area network. If the HBA fails, the server loses its physical connection to the storage fabric, resulting in a complete loss of access to all SAN LUNs for that specific host. The symptoms described, such as all datastores becoming inaccessible on a single host while others remain online, and logs showing I/O timeouts and pathing failures, are classic indicators of an HBA failure. A storage controller failure would impact all connected hosts, not just one. A misconfigured VLAN is a network configuration issue that would likely prevent initial connection rather than cause a sudden failure of an established one. A backplane failure typically affects internally connected components like drives, not the external SAN connection through a specific adapter card.