just a heads up for other ESXi 6 users:
In the latest ESXi patches from November interrupt remapping has been disabled.
In our case this lead to high IO latency (200-400 ms) on one storage path of our QLogic cards when there was high IO for one time because the system was out of interrupt vectors.
Because networking is also affected evacuating a host takes forever. We could "solve" it for a day or so by plugging/inserting the FC cable of the affected path.
Whats so bad about this is that there is not much in the logs about this - the error looks and feels like a cable or hardware fault. Thats why we replaced all cabled / switch ports and it still did not help...
You can re-enable remapping but it might be better to ask VMware if this is safe on your specific hardware...