is nobody going to mention sync writes? Granted this person with their extremely limited knowledge of storage systems would be best to leave such settings alone.
Also EXACLY how is your 4gb network achieved? Is this a LAGG to the switch? Are you simply using MPIO over 4 subnets? are you running 5gb ethernet and reserving 1gb of bandwidth on the interface in vSphere?
Please provide the output of lspci
and ifconfig
from your FreeNAS server.