[Ovirt-devel] Re: NIC bonding and failover...

[Chris Lalancette]

Darryl L. Pierce wrote:
> I'm in the not-an-expert camp as well. But, whe nyou say "expose which
> method" what do you mean there? From my understanding, the way you would
> configure bonding is to load the bonding module and specify which mode to use
> there via "modprobe bonding mode=[#] miimon=[interval]". Is there some

The above is correct.  And, miimon is the preferred way to do *if you can use
it*.  As I understand it, what the miimon method does is to periodically check
the status of the link as the kernel understand it (using the same method that
mii-tool, for instance, would).

However, in blade setups, they tend to have an internal switch that the blades
connect to, and then that switch connects to the outside world.  In this case,
monitoring the status of the link on an individual blade doesn't tell you much;
it only tells you whether you are connected to the internal switch, not if you
are connected to the external network.  In these cases, you actually have to use
the arp_ping method (it's not called that, but something similar).  In this
method, you actually periodically try to reach the "other" path via an ARP
frame, to test your connectivity.  So you would actually load the module like:

modprobe bond mode=# arp_ping=ip arp_interval=xxx

That's what I'm saying you have to expose; the ability to choose miimon
(probably the default), or arp_ping, or another method (there may be more, these
are just the two I know about).

Chris Lalancette