Path failover refers to situations when the active path to a LUN is changed from one path to another, usually because of some SAN component failure along the current path. A server usually has one or two HBAs and each HBA is connected to one or two storage processors on a given SAN array. You can determine the active path, the path currently used by the server, by looking at the LUN’s properties.

When an FC cable is pulled, I/O might pause for 30-60 seconds until the FC driver determines that the link is unavailable and failover has occurred. As a result, the virtual machines, with their virtual disks installed on SAN storage, can appear unresponsive. If you attempt to display the host, its storage devices, or its adapter, the operation might appear to stall. After failover is complete, I/O resumes normally.

In case of disastrous events that include multiple breakages, all connections to SAN storage devices might be lost. If none of the connections to the storage device is working, some virtual machines might encounter I/O errors on their virtual disks.