This is the cumulative link failure events counter: counts how many times this port's physical FC link has gone down and had to reinitialize, i.e. loss-of-light or a failed link-level protocol negotiation. On one specific FC port's current error-statistics object, this is the lifetime tally, so each increment is effectively an outage on that path, so even one non-zero value on a production SAN uplink is worth checking against cabling or SFP work logs. For example, a port reads 0 link failures for months, then logs 1 the same afternoon a chassis was moved to a new rack row and its fiber run was re-terminated.