----- Original Message -----
From: "Itamar Heim" iheim@redhat.com To: "Dan Kenigsberg" danken@redhat.com Cc: "Alon Bar-Lev" alonbl@redhat.com, "VDSM Project Development" vdsm-devel@lists.fedorahosted.org, "Yaniv Kaul" ykaul@redhat.com Sent: Wednesday, November 28, 2012 11:01:35 AM Subject: Re: [vdsm] Future of Vdsm network configuration - Thread mid-summary
On 11/28/2012 03:53 AM, Dan Kenigsberg wrote:
On Tue, Nov 27, 2012 at 03:24:58PM -0500, Alon Bar-Lev wrote:
Management interface configuration is a separate issue.
But it is an important issue that has to be discussed..
If we perform changes of this interface when host is in maintenance we reduce the complexity of the problem.
For your specific issue, if there are two interfaces, one which is up during boot and one which is down during boot, there is no problem to bond them after boot without persisting configuration.
how would you know which bond mode to use? which MTU?
I don't understand the question.
I think I do: Alon suggests that on boot, the management interface would not have bonding at all, and use a single nic. The switch would have to assume that other nics in the bond are dead, and will use the only one which is alive to transfer packets.
There is no doubt that we have to persist the vlan tag of the management interface, and its MTU, in the extremely rare case where the network would not alow Linux's default of 1500.
i was thinking manager may be using jumbo frames to talk to host, and host will have an issue with them since it is set to 1500 instead of 8k. jumbo frames isn't a rare case.
as for bond, are you sure you can use a nic in a non bonded mode for all bond modes?
all bond modes have to cope with a situation where only a single nic is active and the rest are down, so one can boot with a single active nic and only activate the rest and promote to the desired bond mode upon getting the full network configuration from the manager.
Changing the master interface mtu for either vlan or bond is required for management interface and non management interface.
So the logic would probably be set max(mtu(slaves)) regardless it is management interface or not.
I discussed this with Livnat, if there are applications that access the master interface directly we may break them, as the destination may not support non standard mtu.
This is true in current implementation and any future implementation.
It is bad practice to use the master interface directly (mixed tagged/untagged), better to define in switch that untagged communication belongs to vlanX, then use this explicit vlanX at host.
next, what if we're using openvswitch, and you need some flow definitions for the management interface?
I cannot answer that as I don't know openvswitch very well and don't know what "flow definitions" are, however, I do guess that it has non persistent mode that can effect any interface on its control. If you like I can research this one.
you mainly need OVS for provisioning VM networks so here too you can completely bypass OVS during boot and only configure it in a transactional manner upon getting the full network configuration from the manager.
a general question, why would you need to configure VM networks on the host (assuming a persistent cached configuration) upon boot if it cannot talk to the manager? after-all, in this case no resources would be scheduled to run on this host until connection to the manager is restored and up-to-date network configuration is applied.
thanks, Roni