On Thu, Feb 26, 2015 at 9:18 AM, Laurent Wandrebeck < l.wandrebeck@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@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-control...
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-virtualiza...
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.