On Thu, Feb 26, 2015 at 9:18 AM, Laurent Wandrebeck < l.wandrebeck at quelquesmots.fr> wrote: > Hi there, > > I’m working on deploying our new cluster. > Masters have 5×1gbps (i210 and i350, thus using igb.ko), configured with > mtu 9000, 802.3ad. Works fine *but* I can’t get DCB working (pause frame, > aka flow control, which is supported by and enabled on our switches). > > [root at master2 ~]# dcbtool gc eno1 dcb > Command: Get Config > Feature: DCB State > Port: eno1 > Status: Device not capable > > (I get the same with ELRepo 5.2.15 kmod). > Intel datasheet says flow control is available. > Can’t find much about it on the web or in kernel git repo. Could someone > give me a hand ? > > Regards, > Laurent. > DCB requires Priority Flow Control(PFC) aka 802.1Qbb. "Flow Control" is 802.3x. The two are often confused and not compatible. http://www.intel.com/content/www/us/en/ethernet-controllers/ethernet-controller-i350-datasheet.html Mentions "flow control" several times, but never PFC/priority-flow-control/802.1Qbb. PFC capable switches purposefully disable 802.3x flow control. Also PFC has to negotiate between two devices/switches matching QoS/CoS/no-drop policies. Some good reading for beginner PFC knowledge: http://www.cisco.com/c/dam/en/us/solutions/collateral/data-center-virtualization/ieee-802-1-data-center-bridging/at_a_glance_c45-460907.pdf What exactly are you trying to pause? Typically FCoE/iSCSI is set to "no-drop" and Ethernet traffic is paused/dropped in favor of storage traffic. If there is only one type/class/CoS of traffic PFC won't gain much over regular flow control/802.3x. Hope that helps.