If you’ve launched the High Availability Verification Tool before from Unisphere, you might have seen a similar “does not support high availability” message. If everything checked out fine and you are now searching frantically on the interwebs for an answer, don’t worry, you are probably just running an iSCSI configuration with your vSphere environment.
This server [ESX HOST] has only one HBA (host bus adapter) and does not support high availability.
You can safely ignore this error. The issue involves the way the HAVT tests for high availability on a host. The tool is a hold over from a Fiber Channel only world where 2 HBAs were the minimum requirement for high availability status. With iSCSI, even when you have two NIC cards in your ESX hosts, the IQN name is the same for both NICs and the array thinks you have only one adapter and therefore unable to support high availability.
You DO want to check to verify that you are seeing multiple PATHs to the array though from the ESX hosts. For that, look at the properties of the iSCSI software adapter in Storage Adapters on each ESX hosts' configuration tab to validate that you are able to see the appropriate redundant paths per ESX server [usually 8].