[CentOS] Load Average ~0.40 when idle

[Dan Halbert]

You mentioned these are Supermicro X7DBN boards. They use the Intel 
(ESB2/Gilgal) 82563EB Dual-Port Gigabit Ethernet Controller. There's an 
open bug here: https://bugzilla.redhat.com/show_bug.cgi?id=403121, 
"e1000: issues with Intel ESB2/Gilgal (82563EB)". It doesn't describe 
your problem, but complains about other issues with that NIC, and 
references related bugs.